[python] readonly constructors (#9409)

* readonly

* other tests

* doc

* python samples

* model utils

modules/openapi-generator/src/main/resources/python/model.mustache

@@ -17,6 +17,9 @@ from {{packageName}}.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from {{packageName}}.exceptions import ApiAttributeError
+
 {{#models}}
 {{#model}}
 {{#imports}}

modules/openapi-generator/src/main/resources/python/model_templates/invalid_pos_args.mustache

@@ -0,0 +1,9 @@
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )

modules/openapi-generator/src/main/resources/python/model_templates/method_from_openapi_data_composed.mustache

@@ -0,0 +1,66 @@
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """{{classname}} - a model defined in OpenAPI
+
+        Keyword Args:
+{{#requiredVars}}
+{{#defaultValue}}
+            {{name}} ({{{dataType}}}):{{#description}} {{{description}}}.{{/description}} defaults to {{{defaultValue}}}{{#allowableValues}}, must be one of [{{#enumVars}}{{{value}}}, {{/enumVars}}]{{/allowableValues}}  # noqa: E501
+{{/defaultValue}}
+{{^defaultValue}}
+            {{name}} ({{{dataType}}}):{{#description}} {{{description}}}{{/description}}
+{{/defaultValue}}
+{{/requiredVars}}
+{{> model_templates/docstring_init_required_kwargs }}
+{{#optionalVars}}
+            {{name}} ({{{dataType}}}):{{#description}} {{{description}}}.{{/description}} [optional]{{#defaultValue}} if omitted the server will use the default value of {{{defaultValue}}}{{/defaultValue}}  # noqa: E501
+{{/optionalVars}}
+        """
+
+{{#requiredVars}}
+{{#defaultValue}}
+        {{name}} = kwargs.get('{{name}}', {{{defaultValue}}})
+{{/defaultValue}}
+{{/requiredVars}}
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+{{> model_templates/invalid_pos_args }}
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        constant_args = {
+            '_check_type': _check_type,
+            '_path_to_item': _path_to_item,
+            '_spec_property_naming': _spec_property_naming,
+            '_configuration': _configuration,
+            '_visited_composed_classes': self._visited_composed_classes,
+        }
+        composed_info = validate_get_composed_info(
+            constant_args, kwargs, self)
+        self._composed_instances = composed_info[0]
+        self._var_name_to_model_instances = composed_info[1]
+        self._additional_properties_model_instances = composed_info[2]
+        discarded_args = composed_info[3]
+
+        for var_name, var_value in kwargs.items():
+            if var_name in discarded_args and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self._additional_properties_model_instances:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+
+        return self

modules/openapi-generator/src/main/resources/python/model_templates/method_from_openapi_data_normal.mustache

@@ -0,0 +1,17 @@
+{{> model_templates/method_from_openapi_data_shared }}
+
+{{#isEnum}}
+        self.value = value
+{{/isEnum}}
+{{#requiredVars}}
+        self.{{name}} = {{name}}
+{{/requiredVars}}
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self

modules/openapi-generator/src/main/resources/python/model_templates/method_from_openapi_data_shared.mustache

@@ -0,0 +1,49 @@
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls{{#requiredVars}}{{^defaultValue}}, {{name}}{{/defaultValue}}{{/requiredVars}}, *args, **kwargs):  # noqa: E501
+        """{{classname}} - a model defined in OpenAPI
+
+{{#requiredVars}}
+{{#-first}}
+        Args:
+{{/-first}}
+{{^defaultValue}}
+            {{name}} ({{{dataType}}}):{{#description}} {{{description}}}{{/description}}
+{{/defaultValue}}
+{{#-last}}
+
+{{/-last}}
+{{/requiredVars}}
+        Keyword Args:
+{{#requiredVars}}
+{{#defaultValue}}
+            {{name}} ({{{dataType}}}):{{#description}} {{{description}}}.{{/description}} defaults to {{{defaultValue}}}{{#allowableValues}}, must be one of [{{#enumVars}}{{{value}}}, {{/enumVars}}]{{/allowableValues}}  # noqa: E501
+{{/defaultValue}}
+{{/requiredVars}}
+{{> model_templates/docstring_init_required_kwargs }}
+{{#optionalVars}}
+            {{name}} ({{{dataType}}}):{{#description}} {{{description}}}.{{/description}} [optional]{{#defaultValue}} if omitted the server will use the default value of {{{defaultValue}}}{{/defaultValue}}  # noqa: E501
+{{/optionalVars}}
+        """
+
+{{#requiredVars}}
+{{#defaultValue}}
+        {{name}} = kwargs.get('{{name}}', {{{defaultValue}}})
+{{/defaultValue}}
+{{/requiredVars}}
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+{{> model_templates/invalid_pos_args }}
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)

modules/openapi-generator/src/main/resources/python/model_templates/method_from_openapi_data_simple.mustache

@@ -0,0 +1,62 @@
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):
+        """{{classname}} - a model defined in OpenAPI
+
+        Note that value can be passed either in args or in kwargs, but not in both.
+
+        Args:
+            args[0] ({{{dataType}}}):{{#description}} {{{description}}}.{{/description}}{{#defaultValue}} if omitted defaults to {{{defaultValue}}}{{/defaultValue}}{{#allowableValues}}, must be one of [{{#enumVars}}{{{value}}}, {{/enumVars}}]{{/allowableValues}}  # noqa: E501
+
+        Keyword Args:
+            value ({{{dataType}}}):{{#description}} {{{description}}}.{{/description}}{{#defaultValue}} if omitted defaults to {{{defaultValue}}}{{/defaultValue}}{{#allowableValues}}, must be one of [{{#enumVars}}{{{value}}}, {{/enumVars}}]{{/allowableValues}}  # noqa: E501
+{{> model_templates/docstring_init_required_kwargs }}
+        """
+        # required up here when default value is not given
+        _path_to_item = kwargs.pop('_path_to_item', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if 'value' in kwargs:
+            value = kwargs.pop('value')
+        elif args:
+            args = list(args)
+            value = args.pop(0)
+{{#defaultValue}}
+        else:
+            value = {{{defaultValue}}}
+{{/defaultValue}}
+{{^defaultValue}}
+        else:
+            raise ApiTypeError(
+                "value is required, but not passed in args or kwargs and doesn't have default",
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+{{/defaultValue}}
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+{{> model_templates/invalid_pos_args }}
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+        self.value = value
+        if kwargs:
+            raise ApiTypeError(
+                "Invalid named arguments=%s passed to %s. Remove those invalid named arguments." % (
+                    kwargs,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        return self

modules/openapi-generator/src/main/resources/python/model_templates/method_init_composed.mustache

@@ -16,12 +16,14 @@
 
         Keyword Args:
 {{#requiredVars}}
+{{^isReadOnly}}
 {{#defaultValue}}
             {{name}} ({{{dataType}}}):{{#description}} {{{description}}}.{{/description}} defaults to {{{defaultValue}}}{{#allowableValues}}, must be one of [{{#enumVars}}{{{value}}}, {{/enumVars}}]{{/allowableValues}}  # noqa: E501
 {{/defaultValue}}
 {{^defaultValue}}
             {{name}} ({{{dataType}}}):{{#description}} {{{description}}}{{/description}}
 {{/defaultValue}}
+{{/isReadOnly}}
 {{/requiredVars}}
 {{> model_templates/docstring_init_required_kwargs }}
 {{#optionalVars}}
@@ -30,9 +32,11 @@
         """
 
 {{#requiredVars}}
+{{^isReadOnly}}
 {{#defaultValue}}
         {{name}} = kwargs.get('{{name}}', {{{defaultValue}}})
 {{/defaultValue}}
+{{/isReadOnly}}
 {{/requiredVars}}
         _check_type = kwargs.pop('_check_type', True)
         _spec_property_naming = kwargs.pop('_spec_property_naming', False)
@@ -40,15 +44,7 @@
         _configuration = kwargs.pop('_configuration', None)
         _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
 
-        if args:
-            raise ApiTypeError(
-                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
-                    args,
-                    self.__class__.__name__,
-                ),
-                path_to_item=_path_to_item,
-                valid_classes=(self.__class__,),
-            )
+{{> model_templates/invalid_pos_args }}
 
         self._data_store = {}
         self._check_type = _check_type
@@ -78,4 +74,7 @@
                         self._additional_properties_model_instances:
                 # discard variable.
                 continue
-            setattr(self, var_name, var_value)
+            setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

modules/openapi-generator/src/main/resources/python/model_templates/method_init_normal.mustache

@@ -13,7 +13,9 @@
         self.value = value
 {{/isEnum}}
 {{#requiredVars}}
+{{^isReadOnly}}
         self.{{name}} = {{name}}
+{{/isReadOnly}}
 {{/requiredVars}}
         for var_name, var_value in kwargs.items():
             if var_name not in self.attribute_map and \
@@ -22,4 +24,7 @@
                         self.additional_properties_type is None:
                 # discard variable.
                 continue
-            setattr(self, var_name, var_value)
+            setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

modules/openapi-generator/src/main/resources/python/model_templates/method_init_shared.mustache

@@ -1,8 +1,9 @@
     @convert_js_args_to_python_args
-    def __init__(self{{#requiredVars}}{{^defaultValue}}, {{name}}{{/defaultValue}}{{/requiredVars}}, *args, **kwargs):  # noqa: E501
+    def __init__(self{{#requiredVars}}{{^isReadOnly}}{{^defaultValue}}, {{name}}{{/defaultValue}}{{/isReadOnly}}{{/requiredVars}}, *args, **kwargs):  # noqa: E501
         """{{classname}} - a model defined in OpenAPI
 
 {{#requiredVars}}
+{{^isReadOnly}}
 {{#-first}}
         Args:
 {{/-first}}
@@ -12,12 +13,15 @@
 {{#-last}}
 
 {{/-last}}
+{{/isReadOnly}}
 {{/requiredVars}}
         Keyword Args:
 {{#requiredVars}}
+{{^isReadOnly}}
 {{#defaultValue}}
             {{name}} ({{{dataType}}}):{{#description}} {{{description}}}.{{/description}} defaults to {{{defaultValue}}}{{#allowableValues}}, must be one of [{{#enumVars}}{{{value}}}, {{/enumVars}}]{{/allowableValues}}  # noqa: E501
 {{/defaultValue}}
+{{/isReadOnly}}
 {{/requiredVars}}
 {{> model_templates/docstring_init_required_kwargs }}
 {{#optionalVars}}
@@ -26,9 +30,11 @@
         """
 
 {{#requiredVars}}
+{{^isReadOnly}}
 {{#defaultValue}}
         {{name}} = kwargs.get('{{name}}', {{{defaultValue}}})
 {{/defaultValue}}
+{{/isReadOnly}}
 {{/requiredVars}}
         _check_type = kwargs.pop('_check_type', True)
         _spec_property_naming = kwargs.pop('_spec_property_naming', False)
@@ -36,15 +42,7 @@
         _configuration = kwargs.pop('_configuration', None)
         _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
 
-        if args:
-            raise ApiTypeError(
-                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
-                    args,
-                    self.__class__.__name__,
-                ),
-                path_to_item=_path_to_item,
-                valid_classes=(self.__class__,),
-            )
+{{> model_templates/invalid_pos_args }}
 
         self._data_store = {}
         self._check_type = _check_type

modules/openapi-generator/src/main/resources/python/model_templates/method_init_simple.mustache

@@ -46,15 +46,7 @@
         _configuration = kwargs.pop('_configuration', None)
         _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
 
-        if args:
-            raise ApiTypeError(
-                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
-                    args,
-                    self.__class__.__name__,
-                ),
-                path_to_item=_path_to_item,
-                valid_classes=(self.__class__,),
-            )
+{{> model_templates/invalid_pos_args }}
 
         self._data_store = {}
         self._check_type = _check_type

modules/openapi-generator/src/main/resources/python/model_templates/model_composed.mustache

@@ -24,6 +24,21 @@ class {{classname}}(ModelComposed):
 {{/optionalVars}}
     }
 
+    read_only_vars = {
+{{#requiredVars}}
+{{#isReadOnly}}
+        '{{name}}',  # noqa: E501
+{{/isReadOnly}}
+{{/requiredVars}}
+{{#optionalVars}}
+{{#isReadOnly}}
+        '{{name}}',  # noqa: E501
+{{/isReadOnly}}
+{{/optionalVars}}
+    }
+
+{{> model_templates/method_from_openapi_data_composed }}
+
 {{> model_templates/method_init_composed }}
 
     @cached_property

modules/openapi-generator/src/main/resources/python/model_templates/model_normal.mustache

@@ -24,6 +24,21 @@ class {{classname}}(ModelNormal):
 {{/optionalVars}}
     }
 
+    read_only_vars = {
+{{#requiredVars}}
+{{#isReadOnly}}
+        '{{name}}',  # noqa: E501
+{{/isReadOnly}}
+{{/requiredVars}}
+{{#optionalVars}}
+{{#isReadOnly}}
+        '{{name}}',  # noqa: E501
+{{/isReadOnly}}
+{{/optionalVars}}
+    }
+
     _composed_schemas = {}
 
+{{> model_templates/method_from_openapi_data_normal}}
+
 {{> model_templates/method_init_normal}}

modules/openapi-generator/src/main/resources/python/model_templates/model_simple.mustache

@@ -13,6 +13,10 @@ class {{classname}}(ModelSimple):
 
     attribute_map = {}
 
+    read_only_vars = set()
+
     _composed_schemas = None
 
-{{> model_templates/method_init_simple}}
+{{> model_templates/method_init_simple}}
+
+{{> model_templates/method_from_openapi_data_simple}}

modules/openapi-generator/src/main/resources/python/model_utils.mustache

@@ -21,6 +21,22 @@ none_type = type(None)
 file_type = io.IOBase
 
 
+def convert_js_args_to_python_args(fn):
+    from functools import wraps
+    @wraps(fn)
+    def wrapped_init(_self, *args, **kwargs):
+        """
+        An attribute named `self` received from the api will conflicts with the reserved `self`
+        parameter of a class method. During generation, `self` attributes are mapped
+        to `_self` in models. Here, we name `_self` instead of `self` to avoid conflicts.
+        """
+        spec_property_naming = kwargs.get('_spec_property_naming', False)
+        if spec_property_naming:
+            kwargs = change_keys_js_to_python(kwargs, _self if isinstance(_self, type) else _self.__class__)
+        return fn(_self, *args, **kwargs)
+    return wrapped_init
+
+
 class cached_property(object):
     # this caches the result of the function call for fn with no inputs
     # use this as a decorator on fuction methods that you want converted
@@ -212,6 +228,121 @@ class OpenApiModel(object):
         return new_inst
 
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _new_from_openapi_data(cls, *args, **kwargs):
+        # this function uses the discriminator to
+        # pick a new schema/class to instantiate because a discriminator
+        # propertyName value was passed in
+
+        if len(args) == 1:
+            arg = args[0]
+            if arg is None and is_type_nullable(cls):
+                # The input data is the 'null' value and the type is nullable.
+                return None
+
+            if issubclass(cls, ModelComposed) and allows_single_value_input(cls):
+                model_kwargs = {}
+                oneof_instance = get_oneof_instance(cls, model_kwargs, kwargs, model_arg=arg)
+                return oneof_instance
+
+
+        visited_composed_classes = kwargs.get('_visited_composed_classes', ())
+        if (
+            cls.discriminator is None or
+            cls in visited_composed_classes
+        ):
+            # Use case 1: this openapi schema (cls) does not have a discriminator
+            # Use case 2: we have already visited this class before and are sure that we
+            # want to instantiate it this time. We have visited this class deserializing
+            # a payload with a discriminator. During that process we traveled through
+            # this class but did not make an instance of it. Now we are making an
+            # instance of a composed class which contains cls in it, so this time make an instance of cls.
+            #
+            # Here's an example of use case 2: If Animal has a discriminator
+            # petType and we pass in "Dog", and the class Dog
+            # allOf includes Animal, we move through Animal
+            # once using the discriminator, and pick Dog.
+            # Then in the composed schema dog Dog, we will make an instance of the
+            # Animal class (because Dal has allOf: Animal) but this time we won't travel
+            # through Animal's discriminator because we passed in
+            # _visited_composed_classes = (Animal,)
+
+            return cls._from_openapi_data(*args, **kwargs)
+
+        # Get the name and value of the discriminator property.
+        # The discriminator name is obtained from the discriminator meta-data
+        # and the discriminator value is obtained from the input data.
+        discr_propertyname_py = list(cls.discriminator.keys())[0]
+        discr_propertyname_js = cls.attribute_map[discr_propertyname_py]
+        if discr_propertyname_js in kwargs:
+            discr_value = kwargs[discr_propertyname_js]
+        elif discr_propertyname_py in kwargs:
+            discr_value = kwargs[discr_propertyname_py]
+        else:
+            # The input data does not contain the discriminator property.
+            path_to_item = kwargs.get('_path_to_item', ())
+            raise ApiValueError(
+                "Cannot deserialize input data due to missing discriminator. "
+                "The discriminator property '%s' is missing at path: %s" %
+                (discr_propertyname_js, path_to_item)
+            )
+
+        # Implementation note: the last argument to get_discriminator_class
+        # is a list of visited classes. get_discriminator_class may recursively
+        # call itself and update the list of visited classes, and the initial
+        # value must be an empty list. Hence not using 'visited_composed_classes'
+        new_cls = get_discriminator_class(
+                    cls, discr_propertyname_py, discr_value, [])
+        if new_cls is None:
+            path_to_item = kwargs.get('_path_to_item', ())
+            disc_prop_value = kwargs.get(
+                discr_propertyname_js, kwargs.get(discr_propertyname_py))
+            raise ApiValueError(
+                "Cannot deserialize input data due to invalid discriminator "
+                "value. The OpenAPI document has no mapping for discriminator "
+                "property '%s'='%s' at path: %s" %
+                (discr_propertyname_js, disc_prop_value, path_to_item)
+            )
+
+        if new_cls in visited_composed_classes:
+            # if we are making an instance of a composed schema Descendent
+            # which allOf includes Ancestor, then Ancestor contains
+            # a discriminator that includes Descendent.
+            # So if we make an instance of Descendent, we have to make an
+            # instance of Ancestor to hold the allOf properties.
+            # This code detects that use case and makes the instance of Ancestor
+            # For example:
+            # When making an instance of Dog, _visited_composed_classes = (Dog,)
+            # then we make an instance of Animal to include in dog._composed_instances
+            # so when we are here, cls is Animal
+            # cls.discriminator != None
+            # cls not in _visited_composed_classes
+            # new_cls = Dog
+            # but we know we know that we already have Dog
+            # because it is in visited_composed_classes
+            # so make Animal here
+            return cls._from_openapi_data(*args, **kwargs)
+
+        # Build a list containing all oneOf and anyOf descendants.
+        oneof_anyof_classes = None
+        if cls._composed_schemas is not None:
+            oneof_anyof_classes = (
+                cls._composed_schemas.get('oneOf', ()) +
+                cls._composed_schemas.get('anyOf', ()))
+        oneof_anyof_child = new_cls in oneof_anyof_classes
+        kwargs['_visited_composed_classes'] = visited_composed_classes + (cls,)
+
+        if cls._composed_schemas.get('allOf') and oneof_anyof_child:
+            # Validate that we can make self because when we make the
+            # new_cls it will not include the allOf validations in self
+            self_inst = cls._from_openapi_data(*args, **kwargs)
+
+
+        new_inst = new_cls._new_from_openapi_data(*args, **kwargs)
+        return new_inst
+
+
 class ModelSimple(OpenApiModel):
     """the parent class of models whose type != object in their
     swagger/openapi"""
@@ -911,14 +1042,14 @@ def deserialize_model(model_data, model_class, path_to_item, check_type,
                    _spec_property_naming=spec_property_naming)
 
     if issubclass(model_class, ModelSimple):
-        return model_class(model_data, **kw_args)
+        return model_class._new_from_openapi_data(model_data, **kw_args)
     elif isinstance(model_data, list):
-        return model_class(*model_data, **kw_args)
+        return model_class._new_from_openapi_data(*model_data, **kw_args)
     if isinstance(model_data, dict):
         kw_args.update(model_data)
-        return model_class(**kw_args)
+        return model_class._new_from_openapi_data(**kw_args)
     elif isinstance(model_data, PRIMITIVE_TYPES):
-        return model_class(model_data, **kw_args)
+        return model_class._new_from_openapi_data(model_data, **kw_args)
 
 
 def deserialize_file(response_data, configuration, content_disposition=None):
@@ -1280,22 +1411,6 @@ def get_valid_classes_phrase(input_classes):
     return "is one of [{0}]".format(", ".join(all_class_names))
 
 
-def convert_js_args_to_python_args(fn):
-    from functools import wraps
-    @wraps(fn)
-    def wrapped_init(_self, *args, **kwargs):
-        """
-        An attribute named `self` received from the api will conflicts with the reserved `self`
-        parameter of a class method. During generation, `self` attributes are mapped
-        to `_self` in models. Here, we name `_self` instead of `self` to avoid conflicts.
-        """
-        spec_property_naming = kwargs.get('_spec_property_naming', False)
-        if spec_property_naming:
-            kwargs = change_keys_js_to_python(kwargs, _self.__class__)
-        return fn(_self, *args, **kwargs)
-    return wrapped_init
-
-
 def get_allof_instances(self, model_args, constant_args):
     """
     Args:

modules/openapi-generator/src/test/resources/3_0/python/petstore-with-fake-endpoints-models-for-testing-with-http-signature.yaml

@@ -2422,3 +2422,26 @@ components:
                 items:
                   type: string
                   nullable: true
+    Mole:
+      type: object
+      required:
+        - blind
+        - smell
+        - hearing
+      properties:
+        blind:
+          type: boolean
+          readOnly: true
+        smell:
+          type: string
+          readOnly: false
+        touch:
+          type: boolean
+          readOnly: true
+        taste:
+          type: string
+          readOnly: false
+        hearing:
+          type: boolean
+        seeingGhosts:
+          type: boolean

samples/client/petstore/python/petstore_api/model/additional_properties_any_type.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class AdditionalPropertiesAnyType(ModelNormal):
@@ -90,8 +93,85 @@ class AdditionalPropertiesAnyType(ModelNormal):
         'name': 'name',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """AdditionalPropertiesAnyType - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            name (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class AdditionalPropertiesAnyType(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/additional_properties_array.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class AdditionalPropertiesArray(ModelNormal):
@@ -90,8 +93,85 @@ class AdditionalPropertiesArray(ModelNormal):
         'name': 'name',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """AdditionalPropertiesArray - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            name (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class AdditionalPropertiesArray(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/additional_properties_boolean.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class AdditionalPropertiesBoolean(ModelNormal):
@@ -90,8 +93,85 @@ class AdditionalPropertiesBoolean(ModelNormal):
         'name': 'name',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """AdditionalPropertiesBoolean - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            name (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class AdditionalPropertiesBoolean(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/additional_properties_class.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class AdditionalPropertiesClass(ModelNormal):
@@ -110,8 +113,95 @@ class AdditionalPropertiesClass(ModelNormal):
         'anytype_3': 'anytype_3',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """AdditionalPropertiesClass - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            map_string ({str: (str,)}): [optional]  # noqa: E501
+            map_number ({str: (float,)}): [optional]  # noqa: E501
+            map_integer ({str: (int,)}): [optional]  # noqa: E501
+            map_boolean ({str: (bool,)}): [optional]  # noqa: E501
+            map_array_integer ({str: ([int],)}): [optional]  # noqa: E501
+            map_array_anytype ({str: ([bool, date, datetime, dict, float, int, list, str, none_type],)}): [optional]  # noqa: E501
+            map_map_string ({str: ({str: (str,)},)}): [optional]  # noqa: E501
+            map_map_anytype ({str: ({str: (bool, date, datetime, dict, float, int, list, str, none_type,)},)}): [optional]  # noqa: E501
+            anytype_1 (bool, date, datetime, dict, float, int, list, str, none_type): [optional]  # noqa: E501
+            anytype_2 (bool, date, datetime, dict, float, int, list, str, none_type): no type is set for this. [optional]  # noqa: E501
+            anytype_3 (bool, date, datetime, dict, float, int, list, str, none_type): because of a bug in swagger-parser, this should have values {str: (str, int, float...)} but instead we get any type. See https://github.com/swagger-api/swagger-parser/issues/1378. [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -200,3 +290,6 @@ class AdditionalPropertiesClass(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/additional_properties_integer.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class AdditionalPropertiesInteger(ModelNormal):
@@ -90,8 +93,85 @@ class AdditionalPropertiesInteger(ModelNormal):
         'name': 'name',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """AdditionalPropertiesInteger - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            name (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class AdditionalPropertiesInteger(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/additional_properties_number.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class AdditionalPropertiesNumber(ModelNormal):
@@ -90,8 +93,85 @@ class AdditionalPropertiesNumber(ModelNormal):
         'name': 'name',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """AdditionalPropertiesNumber - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            name (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class AdditionalPropertiesNumber(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/additional_properties_object.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class AdditionalPropertiesObject(ModelNormal):
@@ -90,8 +93,85 @@ class AdditionalPropertiesObject(ModelNormal):
         'name': 'name',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """AdditionalPropertiesObject - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            name (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class AdditionalPropertiesObject(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/additional_properties_string.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class AdditionalPropertiesString(ModelNormal):
@@ -90,8 +93,85 @@ class AdditionalPropertiesString(ModelNormal):
         'name': 'name',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """AdditionalPropertiesString - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            name (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class AdditionalPropertiesString(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/animal.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.cat import Cat
@@ -106,8 +109,89 @@ class Animal(ModelNormal):
         'color': 'color',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, class_name, *args, **kwargs):  # noqa: E501
+        """Animal - a model defined in OpenAPI
+
+        Args:
+            class_name (str):
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            color (str): [optional] if omitted the server will use the default value of "red"  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        self.class_name = class_name
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -190,3 +274,6 @@ class Animal(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/animal_farm.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.animal import Animal
@@ -90,6 +93,8 @@ class AnimalFarm(ModelSimple):
 
     attribute_map = {}
 
+    read_only_vars = set()
+
     _composed_schemas = None
 
     required_properties = set([
@@ -189,3 +194,97 @@ class AnimalFarm(ModelSimple):
                 path_to_item=_path_to_item,
                 valid_classes=(self.__class__,),
             )
+
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):
+        """AnimalFarm - a model defined in OpenAPI
+
+        Note that value can be passed either in args or in kwargs, but not in both.
+
+        Args:
+            args[0] ([Animal]):  # noqa: E501
+
+        Keyword Args:
+            value ([Animal]):  # noqa: E501
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+        """
+        # required up here when default value is not given
+        _path_to_item = kwargs.pop('_path_to_item', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if 'value' in kwargs:
+            value = kwargs.pop('value')
+        elif args:
+            args = list(args)
+            value = args.pop(0)
+        else:
+            raise ApiTypeError(
+                "value is required, but not passed in args or kwargs and doesn't have default",
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+        self.value = value
+        if kwargs:
+            raise ApiTypeError(
+                "Invalid named arguments=%s passed to %s. Remove those invalid named arguments." % (
+                    kwargs,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        return self

samples/client/petstore/python/petstore_api/model/api_response.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class ApiResponse(ModelNormal):
@@ -94,8 +97,87 @@ class ApiResponse(ModelNormal):
         'message': 'message',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ApiResponse - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            code (int): [optional]  # noqa: E501
+            type (str): [optional]  # noqa: E501
+            message (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -176,3 +258,6 @@ class ApiResponse(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/array_of_array_of_number_only.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class ArrayOfArrayOfNumberOnly(ModelNormal):
@@ -90,8 +93,85 @@ class ArrayOfArrayOfNumberOnly(ModelNormal):
         'array_array_number': 'ArrayArrayNumber',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ArrayOfArrayOfNumberOnly - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            array_array_number ([[float]]): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class ArrayOfArrayOfNumberOnly(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/array_of_number_only.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class ArrayOfNumberOnly(ModelNormal):
@@ -90,8 +93,85 @@ class ArrayOfNumberOnly(ModelNormal):
         'array_number': 'ArrayNumber',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ArrayOfNumberOnly - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            array_number ([float]): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class ArrayOfNumberOnly(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/array_test.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.read_only_first import ReadOnlyFirst
@@ -100,8 +103,87 @@ class ArrayTest(ModelNormal):
         'array_array_of_model': 'array_array_of_model',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ArrayTest - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            array_of_string ([str]): [optional]  # noqa: E501
+            array_array_of_integer ([[int]]): [optional]  # noqa: E501
+            array_array_of_model ([[ReadOnlyFirst]]): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -182,3 +264,6 @@ class ArrayTest(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/capitalization.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class Capitalization(ModelNormal):
@@ -100,8 +103,90 @@ class Capitalization(ModelNormal):
         'att_name': 'ATT_NAME',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """Capitalization - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            small_camel (str): [optional]  # noqa: E501
+            capital_camel (str): [optional]  # noqa: E501
+            small_snake (str): [optional]  # noqa: E501
+            capital_snake (str): [optional]  # noqa: E501
+            sca_eth_flow_points (str): [optional]  # noqa: E501
+            att_name (str): Name of the pet . [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -185,3 +270,6 @@ class Capitalization(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/cat.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.animal import Animal
@@ -105,6 +108,100 @@ class Cat(ModelComposed):
         'color': 'color',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """Cat - a model defined in OpenAPI
+
+        Keyword Args:
+            class_name (str):
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            declawed (bool): [optional]  # noqa: E501
+            color (str): [optional] if omitted the server will use the default value of "red"  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        constant_args = {
+            '_check_type': _check_type,
+            '_path_to_item': _path_to_item,
+            '_spec_property_naming': _spec_property_naming,
+            '_configuration': _configuration,
+            '_visited_composed_classes': self._visited_composed_classes,
+        }
+        composed_info = validate_get_composed_info(
+            constant_args, kwargs, self)
+        self._composed_instances = composed_info[0]
+        self._var_name_to_model_instances = composed_info[1]
+        self._additional_properties_model_instances = composed_info[2]
+        discarded_args = composed_info[3]
+
+        for var_name, var_value in kwargs.items():
+            if var_name in discarded_args and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self._additional_properties_model_instances:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -202,6 +299,9 @@ class Cat(ModelComposed):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")
 
     @cached_property
     def _composed_schemas():

samples/client/petstore/python/petstore_api/model/cat_all_of.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class CatAllOf(ModelNormal):
@@ -90,8 +93,85 @@ class CatAllOf(ModelNormal):
         'declawed': 'declawed',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """CatAllOf - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            declawed (bool): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class CatAllOf(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/category.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class Category(ModelNormal):
@@ -92,8 +95,90 @@ class Category(ModelNormal):
         'id': 'id',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """Category - a model defined in OpenAPI
+
+        Args:
+
+        Keyword Args:
+            name (str): defaults to "default-name"  # noqa: E501
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            id (int): [optional]  # noqa: E501
+        """
+
+        name = kwargs.get('name', "default-name")
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        self.name = name
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -177,3 +262,6 @@ class Category(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/child.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.child_all_of import ChildAllOf
@@ -102,6 +105,100 @@ class Child(ModelComposed):
         'inter_net': 'interNet',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """Child - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            radio_waves (bool): [optional]  # noqa: E501
+            tele_vision (bool): [optional]  # noqa: E501
+            inter_net (bool): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        constant_args = {
+            '_check_type': _check_type,
+            '_path_to_item': _path_to_item,
+            '_spec_property_naming': _spec_property_naming,
+            '_configuration': _configuration,
+            '_visited_composed_classes': self._visited_composed_classes,
+        }
+        composed_info = validate_get_composed_info(
+            constant_args, kwargs, self)
+        self._composed_instances = composed_info[0]
+        self._var_name_to_model_instances = composed_info[1]
+        self._additional_properties_model_instances = composed_info[2]
+        discarded_args = composed_info[3]
+
+        for var_name, var_value in kwargs.items():
+            if var_name in discarded_args and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self._additional_properties_model_instances:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -199,6 +296,9 @@ class Child(ModelComposed):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")
 
     @cached_property
     def _composed_schemas():

samples/client/petstore/python/petstore_api/model/child_all_of.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class ChildAllOf(ModelNormal):
@@ -90,8 +93,85 @@ class ChildAllOf(ModelNormal):
         'inter_net': 'interNet',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ChildAllOf - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            inter_net (bool): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class ChildAllOf(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/child_cat.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.child_cat_all_of import ChildCatAllOf
@@ -103,6 +106,99 @@ class ChildCat(ModelComposed):
         'name': 'name',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ChildCat - a model defined in OpenAPI
+
+        Keyword Args:
+            pet_type (str):
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            name (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        constant_args = {
+            '_check_type': _check_type,
+            '_path_to_item': _path_to_item,
+            '_spec_property_naming': _spec_property_naming,
+            '_configuration': _configuration,
+            '_visited_composed_classes': self._visited_composed_classes,
+        }
+        composed_info = validate_get_composed_info(
+            constant_args, kwargs, self)
+        self._composed_instances = composed_info[0]
+        self._var_name_to_model_instances = composed_info[1]
+        self._additional_properties_model_instances = composed_info[2]
+        discarded_args = composed_info[3]
+
+        for var_name, var_value in kwargs.items():
+            if var_name in discarded_args and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self._additional_properties_model_instances:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -199,6 +295,9 @@ class ChildCat(ModelComposed):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")
 
     @cached_property
     def _composed_schemas():

samples/client/petstore/python/petstore_api/model/child_cat_all_of.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class ChildCatAllOf(ModelNormal):
@@ -90,8 +93,85 @@ class ChildCatAllOf(ModelNormal):
         'name': 'name',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ChildCatAllOf - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            name (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class ChildCatAllOf(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/child_dog.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.child_dog_all_of import ChildDogAllOf
@@ -103,6 +106,99 @@ class ChildDog(ModelComposed):
         'bark': 'bark',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ChildDog - a model defined in OpenAPI
+
+        Keyword Args:
+            pet_type (str):
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            bark (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        constant_args = {
+            '_check_type': _check_type,
+            '_path_to_item': _path_to_item,
+            '_spec_property_naming': _spec_property_naming,
+            '_configuration': _configuration,
+            '_visited_composed_classes': self._visited_composed_classes,
+        }
+        composed_info = validate_get_composed_info(
+            constant_args, kwargs, self)
+        self._composed_instances = composed_info[0]
+        self._var_name_to_model_instances = composed_info[1]
+        self._additional_properties_model_instances = composed_info[2]
+        discarded_args = composed_info[3]
+
+        for var_name, var_value in kwargs.items():
+            if var_name in discarded_args and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self._additional_properties_model_instances:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -199,6 +295,9 @@ class ChildDog(ModelComposed):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")
 
     @cached_property
     def _composed_schemas():

samples/client/petstore/python/petstore_api/model/child_dog_all_of.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class ChildDogAllOf(ModelNormal):
@@ -90,8 +93,85 @@ class ChildDogAllOf(ModelNormal):
         'bark': 'bark',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ChildDogAllOf - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            bark (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class ChildDogAllOf(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/child_lizard.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.child_lizard_all_of import ChildLizardAllOf
@@ -103,6 +106,99 @@ class ChildLizard(ModelComposed):
         'loves_rocks': 'lovesRocks',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ChildLizard - a model defined in OpenAPI
+
+        Keyword Args:
+            pet_type (str):
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            loves_rocks (bool): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        constant_args = {
+            '_check_type': _check_type,
+            '_path_to_item': _path_to_item,
+            '_spec_property_naming': _spec_property_naming,
+            '_configuration': _configuration,
+            '_visited_composed_classes': self._visited_composed_classes,
+        }
+        composed_info = validate_get_composed_info(
+            constant_args, kwargs, self)
+        self._composed_instances = composed_info[0]
+        self._var_name_to_model_instances = composed_info[1]
+        self._additional_properties_model_instances = composed_info[2]
+        discarded_args = composed_info[3]
+
+        for var_name, var_value in kwargs.items():
+            if var_name in discarded_args and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self._additional_properties_model_instances:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -199,6 +295,9 @@ class ChildLizard(ModelComposed):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")
 
     @cached_property
     def _composed_schemas():

samples/client/petstore/python/petstore_api/model/child_lizard_all_of.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class ChildLizardAllOf(ModelNormal):
@@ -90,8 +93,85 @@ class ChildLizardAllOf(ModelNormal):
         'loves_rocks': 'lovesRocks',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ChildLizardAllOf - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            loves_rocks (bool): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class ChildLizardAllOf(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/class_model.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class ClassModel(ModelNormal):
@@ -90,8 +93,85 @@ class ClassModel(ModelNormal):
         '_class': '_class',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ClassModel - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            _class (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class ClassModel(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/client.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class Client(ModelNormal):
@@ -90,8 +93,85 @@ class Client(ModelNormal):
         'client': 'client',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """Client - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            client (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class Client(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/dog.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.animal import Animal
@@ -105,6 +108,100 @@ class Dog(ModelComposed):
         'color': 'color',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """Dog - a model defined in OpenAPI
+
+        Keyword Args:
+            class_name (str):
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            breed (str): [optional]  # noqa: E501
+            color (str): [optional] if omitted the server will use the default value of "red"  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        constant_args = {
+            '_check_type': _check_type,
+            '_path_to_item': _path_to_item,
+            '_spec_property_naming': _spec_property_naming,
+            '_configuration': _configuration,
+            '_visited_composed_classes': self._visited_composed_classes,
+        }
+        composed_info = validate_get_composed_info(
+            constant_args, kwargs, self)
+        self._composed_instances = composed_info[0]
+        self._var_name_to_model_instances = composed_info[1]
+        self._additional_properties_model_instances = composed_info[2]
+        discarded_args = composed_info[3]
+
+        for var_name, var_value in kwargs.items():
+            if var_name in discarded_args and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self._additional_properties_model_instances:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -202,6 +299,9 @@ class Dog(ModelComposed):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")
 
     @cached_property
     def _composed_schemas():

samples/client/petstore/python/petstore_api/model/dog_all_of.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class DogAllOf(ModelNormal):
@@ -90,8 +93,85 @@ class DogAllOf(ModelNormal):
         'breed': 'breed',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """DogAllOf - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            breed (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class DogAllOf(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/enum_arrays.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class EnumArrays(ModelNormal):
@@ -100,8 +103,86 @@ class EnumArrays(ModelNormal):
         'array_enum': 'array_enum',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """EnumArrays - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            just_symbol (str): [optional]  # noqa: E501
+            array_enum ([str]): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -181,3 +262,6 @@ class EnumArrays(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/enum_class.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class EnumClass(ModelSimple):
@@ -89,6 +92,8 @@ class EnumClass(ModelSimple):
 
     attribute_map = {}
 
+    read_only_vars = set()
+
     _composed_schemas = None
 
     required_properties = set([
@@ -184,3 +189,93 @@ class EnumClass(ModelSimple):
                 path_to_item=_path_to_item,
                 valid_classes=(self.__class__,),
             )
+
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):
+        """EnumClass - a model defined in OpenAPI
+
+        Note that value can be passed either in args or in kwargs, but not in both.
+
+        Args:
+            args[0] (str): if omitted defaults to "-efg", must be one of ["_abc", "-efg", "(xyz)", ]  # noqa: E501
+
+        Keyword Args:
+            value (str): if omitted defaults to "-efg", must be one of ["_abc", "-efg", "(xyz)", ]  # noqa: E501
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+        """
+        # required up here when default value is not given
+        _path_to_item = kwargs.pop('_path_to_item', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if 'value' in kwargs:
+            value = kwargs.pop('value')
+        elif args:
+            args = list(args)
+            value = args.pop(0)
+        else:
+            value = "-efg"
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+        self.value = value
+        if kwargs:
+            raise ApiTypeError(
+                "Invalid named arguments=%s passed to %s. Remove those invalid named arguments." % (
+                    kwargs,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        return self

samples/client/petstore/python/petstore_api/model/enum_test.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.string_enum import StringEnum
@@ -122,8 +125,92 @@ class EnumTest(ModelNormal):
         'string_enum': 'stringEnum',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, enum_string_required, *args, **kwargs):  # noqa: E501
+        """EnumTest - a model defined in OpenAPI
+
+        Args:
+            enum_string_required (str):
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            enum_string (str): [optional]  # noqa: E501
+            enum_integer (int): [optional]  # noqa: E501
+            enum_number (float): [optional]  # noqa: E501
+            string_enum (StringEnum): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        self.enum_string_required = enum_string_required
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -209,3 +296,6 @@ class EnumTest(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/file.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class File(ModelNormal):
@@ -90,8 +93,85 @@ class File(ModelNormal):
         'source_uri': 'sourceURI',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """File - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            source_uri (str): Test capitalization. [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class File(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/file_schema_test_class.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.file import File
@@ -98,8 +101,86 @@ class FileSchemaTestClass(ModelNormal):
         'files': 'files',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """FileSchemaTestClass - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            file (File): [optional]  # noqa: E501
+            files ([File]): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -179,3 +260,6 @@ class FileSchemaTestClass(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/format_test.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class FormatTest(ModelNormal):
@@ -149,8 +152,103 @@ class FormatTest(ModelNormal):
         'uuid': 'uuid',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, number, byte, date, password, *args, **kwargs):  # noqa: E501
+        """FormatTest - a model defined in OpenAPI
+
+        Args:
+            number (float):
+            byte (str):
+            date (date):
+            password (str):
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            integer (int): [optional]  # noqa: E501
+            int32 (int): [optional]  # noqa: E501
+            int64 (int): [optional]  # noqa: E501
+            float (float): [optional]  # noqa: E501
+            double (float): [optional]  # noqa: E501
+            string (str): [optional]  # noqa: E501
+            binary (file_type): [optional]  # noqa: E501
+            date_time (datetime): [optional]  # noqa: E501
+            uuid (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        self.number = number
+        self.byte = byte
+        self.date = date
+        self.password = password
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -247,3 +345,6 @@ class FormatTest(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/grandparent.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class Grandparent(ModelNormal):
@@ -90,8 +93,85 @@ class Grandparent(ModelNormal):
         'radio_waves': 'radioWaves',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """Grandparent - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            radio_waves (bool): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class Grandparent(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/grandparent_animal.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.child_cat import ChildCat
@@ -110,8 +113,88 @@ class GrandparentAnimal(ModelNormal):
         'pet_type': 'pet_type',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, pet_type, *args, **kwargs):  # noqa: E501
+        """GrandparentAnimal - a model defined in OpenAPI
+
+        Args:
+            pet_type (str):
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        self.pet_type = pet_type
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -193,3 +276,6 @@ class GrandparentAnimal(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/has_only_read_only.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class HasOnlyReadOnly(ModelNormal):
@@ -92,8 +95,88 @@ class HasOnlyReadOnly(ModelNormal):
         'foo': 'foo',  # noqa: E501
     }
 
+    read_only_vars = {
+        'bar',  # noqa: E501
+        'foo',  # noqa: E501
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """HasOnlyReadOnly - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            bar (str): [optional]  # noqa: E501
+            foo (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -173,3 +256,6 @@ class HasOnlyReadOnly(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/list.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class List(ModelNormal):
@@ -90,8 +93,85 @@ class List(ModelNormal):
         '_123_list': '123-list',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """List - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            _123_list (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class List(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/map_test.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.string_boolean_map import StringBooleanMap
@@ -106,8 +109,88 @@ class MapTest(ModelNormal):
         'indirect_map': 'indirect_map',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """MapTest - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            map_map_of_string ({str: ({str: (str,)},)}): [optional]  # noqa: E501
+            map_of_enum_string ({str: (str,)}): [optional]  # noqa: E501
+            direct_map ({str: (bool,)}): [optional]  # noqa: E501
+            indirect_map (StringBooleanMap): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -189,3 +272,6 @@ class MapTest(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/mixed_properties_and_additional_properties_class.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.animal import Animal
@@ -100,8 +103,87 @@ class MixedPropertiesAndAdditionalPropertiesClass(ModelNormal):
         'map': 'map',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """MixedPropertiesAndAdditionalPropertiesClass - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            uuid (str): [optional]  # noqa: E501
+            date_time (datetime): [optional]  # noqa: E501
+            map ({str: (Animal,)}): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -182,3 +264,6 @@ class MixedPropertiesAndAdditionalPropertiesClass(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/model200_response.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class Model200Response(ModelNormal):
@@ -92,8 +95,86 @@ class Model200Response(ModelNormal):
         '_class': 'class',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """Model200Response - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            name (int): [optional]  # noqa: E501
+            _class (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -173,3 +254,6 @@ class Model200Response(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/model_return.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class ModelReturn(ModelNormal):
@@ -90,8 +93,85 @@ class ModelReturn(ModelNormal):
         '_return': 'return',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ModelReturn - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            _return (int): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class ModelReturn(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/name.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class Name(ModelNormal):
@@ -96,8 +99,93 @@ class Name(ModelNormal):
         '_123_number': '123Number',  # noqa: E501
     }
 
+    read_only_vars = {
+        'snake_case',  # noqa: E501
+        '_123_number',  # noqa: E501
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, name, *args, **kwargs):  # noqa: E501
+        """Name - a model defined in OpenAPI
+
+        Args:
+            name (int):
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            snake_case (int): [optional]  # noqa: E501
+            _property (str): [optional]  # noqa: E501
+            _123_number (int): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        self.name = name
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -182,3 +270,6 @@ class Name(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/number_only.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class NumberOnly(ModelNormal):
@@ -90,8 +93,85 @@ class NumberOnly(ModelNormal):
         'just_number': 'JustNumber',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """NumberOnly - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            just_number (float): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class NumberOnly(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/number_with_validations.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class NumberWithValidations(ModelSimple):
@@ -88,6 +91,8 @@ class NumberWithValidations(ModelSimple):
 
     attribute_map = {}
 
+    read_only_vars = set()
+
     _composed_schemas = None
 
     required_properties = set([
@@ -187,3 +192,97 @@ class NumberWithValidations(ModelSimple):
                 path_to_item=_path_to_item,
                 valid_classes=(self.__class__,),
             )
+
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):
+        """NumberWithValidations - a model defined in OpenAPI
+
+        Note that value can be passed either in args or in kwargs, but not in both.
+
+        Args:
+            args[0] (float):  # noqa: E501
+
+        Keyword Args:
+            value (float):  # noqa: E501
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+        """
+        # required up here when default value is not given
+        _path_to_item = kwargs.pop('_path_to_item', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if 'value' in kwargs:
+            value = kwargs.pop('value')
+        elif args:
+            args = list(args)
+            value = args.pop(0)
+        else:
+            raise ApiTypeError(
+                "value is required, but not passed in args or kwargs and doesn't have default",
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+        self.value = value
+        if kwargs:
+            raise ApiTypeError(
+                "Invalid named arguments=%s passed to %s. Remove those invalid named arguments." % (
+                    kwargs,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        return self

samples/client/petstore/python/petstore_api/model/object_model_with_ref_props.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.number_with_validations import NumberWithValidations
@@ -100,8 +103,87 @@ class ObjectModelWithRefProps(ModelNormal):
         'my_boolean': 'my_boolean',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ObjectModelWithRefProps - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            my_number (NumberWithValidations): [optional]  # noqa: E501
+            my_string (str): [optional]  # noqa: E501
+            my_boolean (bool): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -182,3 +264,6 @@ class ObjectModelWithRefProps(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/order.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class Order(ModelNormal):
@@ -105,8 +108,90 @@ class Order(ModelNormal):
         'complete': 'complete',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """Order - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            id (int): [optional]  # noqa: E501
+            pet_id (int): [optional]  # noqa: E501
+            quantity (int): [optional]  # noqa: E501
+            ship_date (datetime): [optional]  # noqa: E501
+            status (str): Order Status. [optional]  # noqa: E501
+            complete (bool): [optional] if omitted the server will use the default value of False  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -190,3 +275,6 @@ class Order(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/parent.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.grandparent import Grandparent
@@ -100,6 +103,99 @@ class Parent(ModelComposed):
         'tele_vision': 'teleVision',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """Parent - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            radio_waves (bool): [optional]  # noqa: E501
+            tele_vision (bool): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        constant_args = {
+            '_check_type': _check_type,
+            '_path_to_item': _path_to_item,
+            '_spec_property_naming': _spec_property_naming,
+            '_configuration': _configuration,
+            '_visited_composed_classes': self._visited_composed_classes,
+        }
+        composed_info = validate_get_composed_info(
+            constant_args, kwargs, self)
+        self._composed_instances = composed_info[0]
+        self._var_name_to_model_instances = composed_info[1]
+        self._additional_properties_model_instances = composed_info[2]
+        discarded_args = composed_info[3]
+
+        for var_name, var_value in kwargs.items():
+            if var_name in discarded_args and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self._additional_properties_model_instances:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -196,6 +292,9 @@ class Parent(ModelComposed):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")
 
     @cached_property
     def _composed_schemas():

samples/client/petstore/python/petstore_api/model/parent_all_of.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class ParentAllOf(ModelNormal):
@@ -90,8 +93,85 @@ class ParentAllOf(ModelNormal):
         'tele_vision': 'teleVision',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ParentAllOf - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            tele_vision (bool): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class ParentAllOf(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/parent_pet.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.child_cat import ChildCat
@@ -109,6 +112,98 @@ class ParentPet(ModelComposed):
         'pet_type': 'pet_type',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ParentPet - a model defined in OpenAPI
+
+        Keyword Args:
+            pet_type (str):
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        constant_args = {
+            '_check_type': _check_type,
+            '_path_to_item': _path_to_item,
+            '_spec_property_naming': _spec_property_naming,
+            '_configuration': _configuration,
+            '_visited_composed_classes': self._visited_composed_classes,
+        }
+        composed_info = validate_get_composed_info(
+            constant_args, kwargs, self)
+        self._composed_instances = composed_info[0]
+        self._var_name_to_model_instances = composed_info[1]
+        self._additional_properties_model_instances = composed_info[2]
+        discarded_args = composed_info[3]
+
+        for var_name, var_value in kwargs.items():
+            if var_name in discarded_args and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self._additional_properties_model_instances:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -204,6 +299,9 @@ class ParentPet(ModelComposed):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")
 
     @cached_property
     def _composed_schemas():

samples/client/petstore/python/petstore_api/model/pet.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.category import Category
@@ -113,8 +116,94 @@ class Pet(ModelNormal):
         'status': 'status',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, name, photo_urls, *args, **kwargs):  # noqa: E501
+        """Pet - a model defined in OpenAPI
+
+        Args:
+            name (str):
+            photo_urls ([str]):
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            id (int): [optional]  # noqa: E501
+            category (Category): [optional]  # noqa: E501
+            tags ([Tag]): [optional]  # noqa: E501
+            status (str): pet status in the store. [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        self.name = name
+        self.photo_urls = photo_urls
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -202,3 +291,6 @@ class Pet(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/player.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class Player(ModelNormal):
@@ -92,8 +95,89 @@ class Player(ModelNormal):
         'enemy_player': 'enemyPlayer',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, name, *args, **kwargs):  # noqa: E501
+        """Player - a model defined in OpenAPI
+
+        Args:
+            name (str):
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            enemy_player (Player): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        self.name = name
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -176,3 +260,6 @@ class Player(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/read_only_first.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class ReadOnlyFirst(ModelNormal):
@@ -92,8 +95,87 @@ class ReadOnlyFirst(ModelNormal):
         'baz': 'baz',  # noqa: E501
     }
 
+    read_only_vars = {
+        'bar',  # noqa: E501
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ReadOnlyFirst - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            bar (str): [optional]  # noqa: E501
+            baz (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -173,3 +255,6 @@ class ReadOnlyFirst(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/special_model_name.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class SpecialModelName(ModelNormal):
@@ -90,8 +93,85 @@ class SpecialModelName(ModelNormal):
         'special_property_name': '$special[property.name]',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """SpecialModelName - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            special_property_name (int): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class SpecialModelName(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/string_boolean_map.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class StringBooleanMap(ModelNormal):
@@ -88,8 +91,84 @@ class StringBooleanMap(ModelNormal):
     attribute_map = {
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """StringBooleanMap - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -167,3 +246,6 @@ class StringBooleanMap(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/string_enum.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class StringEnum(ModelSimple):
@@ -89,6 +92,8 @@ class StringEnum(ModelSimple):
 
     attribute_map = {}
 
+    read_only_vars = set()
+
     _composed_schemas = None
 
     required_properties = set([
@@ -188,3 +193,97 @@ class StringEnum(ModelSimple):
                 path_to_item=_path_to_item,
                 valid_classes=(self.__class__,),
             )
+
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):
+        """StringEnum - a model defined in OpenAPI
+
+        Note that value can be passed either in args or in kwargs, but not in both.
+
+        Args:
+            args[0] (str):, must be one of ["placed", "approved", "delivered", ]  # noqa: E501
+
+        Keyword Args:
+            value (str):, must be one of ["placed", "approved", "delivered", ]  # noqa: E501
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+        """
+        # required up here when default value is not given
+        _path_to_item = kwargs.pop('_path_to_item', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if 'value' in kwargs:
+            value = kwargs.pop('value')
+        elif args:
+            args = list(args)
+            value = args.pop(0)
+        else:
+            raise ApiTypeError(
+                "value is required, but not passed in args or kwargs and doesn't have default",
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+        self.value = value
+        if kwargs:
+            raise ApiTypeError(
+                "Invalid named arguments=%s passed to %s. Remove those invalid named arguments." % (
+                    kwargs,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        return self

samples/client/petstore/python/petstore_api/model/tag.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class Tag(ModelNormal):
@@ -94,8 +97,87 @@ class Tag(ModelNormal):
         'full_name': 'fullName',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """Tag - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            id (int): [optional]  # noqa: E501
+            name (str): [optional]  # noqa: E501
+            full_name (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -176,3 +258,6 @@ class Tag(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/type_holder_default.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class TypeHolderDefault(ModelNormal):
@@ -102,8 +105,102 @@ class TypeHolderDefault(ModelNormal):
         'datetime_item': 'datetime_item',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, array_item, *args, **kwargs):  # noqa: E501
+        """TypeHolderDefault - a model defined in OpenAPI
+
+        Args:
+            array_item ([int]):
+
+        Keyword Args:
+            string_item (str): defaults to "what"  # noqa: E501
+            number_item (float): defaults to 1.234  # noqa: E501
+            integer_item (int): defaults to -2  # noqa: E501
+            bool_item (bool): defaults to True  # noqa: E501
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            date_item (date): [optional]  # noqa: E501
+            datetime_item (datetime): [optional]  # noqa: E501
+        """
+
+        string_item = kwargs.get('string_item', "what")
+        number_item = kwargs.get('number_item', 1.234)
+        integer_item = kwargs.get('integer_item', -2)
+        bool_item = kwargs.get('bool_item', True)
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        self.string_item = string_item
+        self.number_item = number_item
+        self.integer_item = integer_item
+        self.bool_item = bool_item
+        self.array_item = array_item
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -199,3 +296,6 @@ class TypeHolderDefault(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/type_holder_example.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class TypeHolderExample(ModelNormal):
@@ -107,8 +110,99 @@ class TypeHolderExample(ModelNormal):
         'array_item': 'array_item',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, bool_item, array_item, *args, **kwargs):  # noqa: E501
+        """TypeHolderExample - a model defined in OpenAPI
+
+        Args:
+            bool_item (bool):
+            array_item ([int]):
+
+        Keyword Args:
+            string_item (str): defaults to "what", must be one of ["what", ]  # noqa: E501
+            number_item (float): defaults to 1.234, must be one of [1.234, ]  # noqa: E501
+            integer_item (int): defaults to -2, must be one of [-2, ]  # noqa: E501
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+        """
+
+        string_item = kwargs.get('string_item', "what")
+        number_item = kwargs.get('number_item', 1.234)
+        integer_item = kwargs.get('integer_item', -2)
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        self.string_item = string_item
+        self.number_item = number_item
+        self.integer_item = integer_item
+        self.bool_item = bool_item
+        self.array_item = array_item
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -201,3 +295,6 @@ class TypeHolderExample(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/user.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class User(ModelNormal):
@@ -104,8 +107,92 @@ class User(ModelNormal):
         'user_status': 'userStatus',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """User - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            id (int): [optional]  # noqa: E501
+            username (str): [optional]  # noqa: E501
+            first_name (str): [optional]  # noqa: E501
+            last_name (str): [optional]  # noqa: E501
+            email (str): [optional]  # noqa: E501
+            password (str): [optional]  # noqa: E501
+            phone (str): [optional]  # noqa: E501
+            user_status (int): User Status. [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -191,3 +278,6 @@ class User(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model/xml_item.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class XmlItem(ModelNormal):
@@ -146,8 +149,113 @@ class XmlItem(ModelNormal):
         'prefix_ns_wrapped_array': 'prefix_ns_wrapped_array',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """XmlItem - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            attribute_string (str): [optional]  # noqa: E501
+            attribute_number (float): [optional]  # noqa: E501
+            attribute_integer (int): [optional]  # noqa: E501
+            attribute_boolean (bool): [optional]  # noqa: E501
+            wrapped_array ([int]): [optional]  # noqa: E501
+            name_string (str): [optional]  # noqa: E501
+            name_number (float): [optional]  # noqa: E501
+            name_integer (int): [optional]  # noqa: E501
+            name_boolean (bool): [optional]  # noqa: E501
+            name_array ([int]): [optional]  # noqa: E501
+            name_wrapped_array ([int]): [optional]  # noqa: E501
+            prefix_string (str): [optional]  # noqa: E501
+            prefix_number (float): [optional]  # noqa: E501
+            prefix_integer (int): [optional]  # noqa: E501
+            prefix_boolean (bool): [optional]  # noqa: E501
+            prefix_array ([int]): [optional]  # noqa: E501
+            prefix_wrapped_array ([int]): [optional]  # noqa: E501
+            namespace_string (str): [optional]  # noqa: E501
+            namespace_number (float): [optional]  # noqa: E501
+            namespace_integer (int): [optional]  # noqa: E501
+            namespace_boolean (bool): [optional]  # noqa: E501
+            namespace_array ([int]): [optional]  # noqa: E501
+            namespace_wrapped_array ([int]): [optional]  # noqa: E501
+            prefix_ns_string (str): [optional]  # noqa: E501
+            prefix_ns_number (float): [optional]  # noqa: E501
+            prefix_ns_integer (int): [optional]  # noqa: E501
+            prefix_ns_boolean (bool): [optional]  # noqa: E501
+            prefix_ns_array ([int]): [optional]  # noqa: E501
+            prefix_ns_wrapped_array ([int]): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -254,3 +362,6 @@ class XmlItem(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python/petstore_api/model_utils.py

@@ -29,6 +29,22 @@ none_type = type(None)
 file_type = io.IOBase
 
 
+def convert_js_args_to_python_args(fn):
+    from functools import wraps
+    @wraps(fn)
+    def wrapped_init(_self, *args, **kwargs):
+        """
+        An attribute named `self` received from the api will conflicts with the reserved `self`
+        parameter of a class method. During generation, `self` attributes are mapped
+        to `_self` in models. Here, we name `_self` instead of `self` to avoid conflicts.
+        """
+        spec_property_naming = kwargs.get('_spec_property_naming', False)
+        if spec_property_naming:
+            kwargs = change_keys_js_to_python(kwargs, _self if isinstance(_self, type) else _self.__class__)
+        return fn(_self, *args, **kwargs)
+    return wrapped_init
+
+
 class cached_property(object):
     # this caches the result of the function call for fn with no inputs
     # use this as a decorator on fuction methods that you want converted
@@ -284,6 +300,121 @@ class OpenApiModel(object):
         return new_inst
 
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _new_from_openapi_data(cls, *args, **kwargs):
+        # this function uses the discriminator to
+        # pick a new schema/class to instantiate because a discriminator
+        # propertyName value was passed in
+
+        if len(args) == 1:
+            arg = args[0]
+            if arg is None and is_type_nullable(cls):
+                # The input data is the 'null' value and the type is nullable.
+                return None
+
+            if issubclass(cls, ModelComposed) and allows_single_value_input(cls):
+                model_kwargs = {}
+                oneof_instance = get_oneof_instance(cls, model_kwargs, kwargs, model_arg=arg)
+                return oneof_instance
+
+
+        visited_composed_classes = kwargs.get('_visited_composed_classes', ())
+        if (
+            cls.discriminator is None or
+            cls in visited_composed_classes
+        ):
+            # Use case 1: this openapi schema (cls) does not have a discriminator
+            # Use case 2: we have already visited this class before and are sure that we
+            # want to instantiate it this time. We have visited this class deserializing
+            # a payload with a discriminator. During that process we traveled through
+            # this class but did not make an instance of it. Now we are making an
+            # instance of a composed class which contains cls in it, so this time make an instance of cls.
+            #
+            # Here's an example of use case 2: If Animal has a discriminator
+            # petType and we pass in "Dog", and the class Dog
+            # allOf includes Animal, we move through Animal
+            # once using the discriminator, and pick Dog.
+            # Then in the composed schema dog Dog, we will make an instance of the
+            # Animal class (because Dal has allOf: Animal) but this time we won't travel
+            # through Animal's discriminator because we passed in
+            # _visited_composed_classes = (Animal,)
+
+            return cls._from_openapi_data(*args, **kwargs)
+
+        # Get the name and value of the discriminator property.
+        # The discriminator name is obtained from the discriminator meta-data
+        # and the discriminator value is obtained from the input data.
+        discr_propertyname_py = list(cls.discriminator.keys())[0]
+        discr_propertyname_js = cls.attribute_map[discr_propertyname_py]
+        if discr_propertyname_js in kwargs:
+            discr_value = kwargs[discr_propertyname_js]
+        elif discr_propertyname_py in kwargs:
+            discr_value = kwargs[discr_propertyname_py]
+        else:
+            # The input data does not contain the discriminator property.
+            path_to_item = kwargs.get('_path_to_item', ())
+            raise ApiValueError(
+                "Cannot deserialize input data due to missing discriminator. "
+                "The discriminator property '%s' is missing at path: %s" %
+                (discr_propertyname_js, path_to_item)
+            )
+
+        # Implementation note: the last argument to get_discriminator_class
+        # is a list of visited classes. get_discriminator_class may recursively
+        # call itself and update the list of visited classes, and the initial
+        # value must be an empty list. Hence not using 'visited_composed_classes'
+        new_cls = get_discriminator_class(
+                    cls, discr_propertyname_py, discr_value, [])
+        if new_cls is None:
+            path_to_item = kwargs.get('_path_to_item', ())
+            disc_prop_value = kwargs.get(
+                discr_propertyname_js, kwargs.get(discr_propertyname_py))
+            raise ApiValueError(
+                "Cannot deserialize input data due to invalid discriminator "
+                "value. The OpenAPI document has no mapping for discriminator "
+                "property '%s'='%s' at path: %s" %
+                (discr_propertyname_js, disc_prop_value, path_to_item)
+            )
+
+        if new_cls in visited_composed_classes:
+            # if we are making an instance of a composed schema Descendent
+            # which allOf includes Ancestor, then Ancestor contains
+            # a discriminator that includes Descendent.
+            # So if we make an instance of Descendent, we have to make an
+            # instance of Ancestor to hold the allOf properties.
+            # This code detects that use case and makes the instance of Ancestor
+            # For example:
+            # When making an instance of Dog, _visited_composed_classes = (Dog,)
+            # then we make an instance of Animal to include in dog._composed_instances
+            # so when we are here, cls is Animal
+            # cls.discriminator != None
+            # cls not in _visited_composed_classes
+            # new_cls = Dog
+            # but we know we know that we already have Dog
+            # because it is in visited_composed_classes
+            # so make Animal here
+            return cls._from_openapi_data(*args, **kwargs)
+
+        # Build a list containing all oneOf and anyOf descendants.
+        oneof_anyof_classes = None
+        if cls._composed_schemas is not None:
+            oneof_anyof_classes = (
+                cls._composed_schemas.get('oneOf', ()) +
+                cls._composed_schemas.get('anyOf', ()))
+        oneof_anyof_child = new_cls in oneof_anyof_classes
+        kwargs['_visited_composed_classes'] = visited_composed_classes + (cls,)
+
+        if cls._composed_schemas.get('allOf') and oneof_anyof_child:
+            # Validate that we can make self because when we make the
+            # new_cls it will not include the allOf validations in self
+            self_inst = cls._from_openapi_data(*args, **kwargs)
+
+
+        new_inst = new_cls._new_from_openapi_data(*args, **kwargs)
+        return new_inst
+
+
 class ModelSimple(OpenApiModel):
     """the parent class of models whose type != object in their
     swagger/openapi"""
@@ -1208,14 +1339,14 @@ def deserialize_model(model_data, model_class, path_to_item, check_type,
                    _spec_property_naming=spec_property_naming)
 
     if issubclass(model_class, ModelSimple):
-        return model_class(model_data, **kw_args)
+        return model_class._new_from_openapi_data(model_data, **kw_args)
     elif isinstance(model_data, list):
-        return model_class(*model_data, **kw_args)
+        return model_class._new_from_openapi_data(*model_data, **kw_args)
     if isinstance(model_data, dict):
         kw_args.update(model_data)
-        return model_class(**kw_args)
+        return model_class._new_from_openapi_data(**kw_args)
     elif isinstance(model_data, PRIMITIVE_TYPES):
-        return model_class(model_data, **kw_args)
+        return model_class._new_from_openapi_data(model_data, **kw_args)
 
 
 def deserialize_file(response_data, configuration, content_disposition=None):
@@ -1577,22 +1708,6 @@ def get_valid_classes_phrase(input_classes):
     return "is one of [{0}]".format(", ".join(all_class_names))
 
 
-def convert_js_args_to_python_args(fn):
-    from functools import wraps
-    @wraps(fn)
-    def wrapped_init(_self, *args, **kwargs):
-        """
-        An attribute named `self` received from the api will conflicts with the reserved `self`
-        parameter of a class method. During generation, `self` attributes are mapped
-        to `_self` in models. Here, we name `_self` instead of `self` to avoid conflicts.
-        """
-        spec_property_naming = kwargs.get('_spec_property_naming', False)
-        if spec_property_naming:
-            kwargs = change_keys_js_to_python(kwargs, _self.__class__)
-        return fn(_self, *args, **kwargs)
-    return wrapped_init
-
-
 def get_allof_instances(self, model_args, constant_args):
     """
     Args:

samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent/petstore_api/model/additional_properties_any_type.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class AdditionalPropertiesAnyType(ModelNormal):
@@ -90,8 +93,85 @@ class AdditionalPropertiesAnyType(ModelNormal):
         'name': 'name',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """AdditionalPropertiesAnyType - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            name (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class AdditionalPropertiesAnyType(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent/petstore_api/model/additional_properties_array.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class AdditionalPropertiesArray(ModelNormal):
@@ -90,8 +93,85 @@ class AdditionalPropertiesArray(ModelNormal):
         'name': 'name',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """AdditionalPropertiesArray - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            name (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class AdditionalPropertiesArray(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent/petstore_api/model/additional_properties_boolean.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class AdditionalPropertiesBoolean(ModelNormal):
@@ -90,8 +93,85 @@ class AdditionalPropertiesBoolean(ModelNormal):
         'name': 'name',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """AdditionalPropertiesBoolean - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            name (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class AdditionalPropertiesBoolean(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent/petstore_api/model/additional_properties_class.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class AdditionalPropertiesClass(ModelNormal):
@@ -104,8 +107,95 @@ class AdditionalPropertiesClass(ModelNormal):
         'anytype_3': 'anytype_3',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """AdditionalPropertiesClass - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            map_string ({str: (str,)}): [optional]  # noqa: E501
+            map_number ({str: (float,)}): [optional]  # noqa: E501
+            map_integer ({str: (int,)}): [optional]  # noqa: E501
+            map_boolean ({str: (bool,)}): [optional]  # noqa: E501
+            map_array_integer ({str: ([int],)}): [optional]  # noqa: E501
+            map_array_anytype ({str: ([bool, date, datetime, dict, float, int, list, str, none_type],)}): [optional]  # noqa: E501
+            map_map_string ({str: ({str: (str,)},)}): [optional]  # noqa: E501
+            map_map_anytype ({str: ({str: (bool, date, datetime, dict, float, int, list, str, none_type,)},)}): [optional]  # noqa: E501
+            anytype_1 (bool, date, datetime, dict, float, int, list, str, none_type): [optional]  # noqa: E501
+            anytype_2 (bool, date, datetime, dict, float, int, list, str, none_type): no type is set for this. [optional]  # noqa: E501
+            anytype_3 (bool, date, datetime, dict, float, int, list, str, none_type): because of a bug in swagger-parser, this should have values {str: (str, int, float...)} but instead we get any type. See https://github.com/swagger-api/swagger-parser/issues/1378. [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -194,3 +284,6 @@ class AdditionalPropertiesClass(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent/petstore_api/model/additional_properties_integer.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class AdditionalPropertiesInteger(ModelNormal):
@@ -90,8 +93,85 @@ class AdditionalPropertiesInteger(ModelNormal):
         'name': 'name',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """AdditionalPropertiesInteger - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            name (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class AdditionalPropertiesInteger(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent/petstore_api/model/additional_properties_number.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class AdditionalPropertiesNumber(ModelNormal):
@@ -90,8 +93,85 @@ class AdditionalPropertiesNumber(ModelNormal):
         'name': 'name',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """AdditionalPropertiesNumber - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            name (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class AdditionalPropertiesNumber(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent/petstore_api/model/additional_properties_object.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class AdditionalPropertiesObject(ModelNormal):
@@ -90,8 +93,85 @@ class AdditionalPropertiesObject(ModelNormal):
         'name': 'name',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """AdditionalPropertiesObject - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            name (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class AdditionalPropertiesObject(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent/petstore_api/model/additional_properties_string.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class AdditionalPropertiesString(ModelNormal):
@@ -90,8 +93,85 @@ class AdditionalPropertiesString(ModelNormal):
         'name': 'name',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """AdditionalPropertiesString - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            name (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +250,6 @@ class AdditionalPropertiesString(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent/petstore_api/model/animal.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.cat import Cat
@@ -99,8 +102,89 @@ class Animal(ModelNormal):
         'color': 'color',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, class_name, *args, **kwargs):  # noqa: E501
+        """Animal - a model defined in OpenAPI
+
+        Args:
+            class_name (str):
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            color (str): [optional] if omitted the server will use the default value of "red"  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        self.class_name = class_name
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -183,3 +267,6 @@ class Animal(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent/petstore_api/model/animal_farm.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.animal import Animal
@@ -83,6 +86,8 @@ class AnimalFarm(ModelSimple):
 
     attribute_map = {}
 
+    read_only_vars = set()
+
     _composed_schemas = None
 
     required_properties = set([
@@ -182,3 +187,97 @@ class AnimalFarm(ModelSimple):
                 path_to_item=_path_to_item,
                 valid_classes=(self.__class__,),
             )
+
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):
+        """AnimalFarm - a model defined in OpenAPI
+
+        Note that value can be passed either in args or in kwargs, but not in both.
+
+        Args:
+            args[0] ([Animal]):  # noqa: E501
+
+        Keyword Args:
+            value ([Animal]):  # noqa: E501
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+        """
+        # required up here when default value is not given
+        _path_to_item = kwargs.pop('_path_to_item', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if 'value' in kwargs:
+            value = kwargs.pop('value')
+        elif args:
+            args = list(args)
+            value = args.pop(0)
+        else:
+            raise ApiTypeError(
+                "value is required, but not passed in args or kwargs and doesn't have default",
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+        self.value = value
+        if kwargs:
+            raise ApiTypeError(
+                "Invalid named arguments=%s passed to %s. Remove those invalid named arguments." % (
+                    kwargs,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        return self

samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent/petstore_api/model/api_response.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class ApiResponse(ModelNormal):
@@ -88,8 +91,87 @@ class ApiResponse(ModelNormal):
         'message': 'message',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ApiResponse - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            code (int): [optional]  # noqa: E501
+            type (str): [optional]  # noqa: E501
+            message (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -170,3 +252,6 @@ class ApiResponse(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent/petstore_api/model/array_of_array_of_number_only.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class ArrayOfArrayOfNumberOnly(ModelNormal):
@@ -84,8 +87,85 @@ class ArrayOfArrayOfNumberOnly(ModelNormal):
         'array_array_number': 'ArrayArrayNumber',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ArrayOfArrayOfNumberOnly - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            array_array_number ([[float]]): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -164,3 +244,6 @@ class ArrayOfArrayOfNumberOnly(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent/petstore_api/model/array_of_number_only.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class ArrayOfNumberOnly(ModelNormal):
@@ -84,8 +87,85 @@ class ArrayOfNumberOnly(ModelNormal):
         'array_number': 'ArrayNumber',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ArrayOfNumberOnly - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            array_number ([float]): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -164,3 +244,6 @@ class ArrayOfNumberOnly(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent/petstore_api/model/array_test.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.read_only_first import ReadOnlyFirst
@@ -93,8 +96,87 @@ class ArrayTest(ModelNormal):
         'array_array_of_model': 'array_array_of_model',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ArrayTest - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            array_of_string ([str]): [optional]  # noqa: E501
+            array_array_of_integer ([[int]]): [optional]  # noqa: E501
+            array_array_of_model ([[ReadOnlyFirst]]): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -175,3 +257,6 @@ class ArrayTest(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent/petstore_api/model/capitalization.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class Capitalization(ModelNormal):
@@ -94,8 +97,90 @@ class Capitalization(ModelNormal):
         'att_name': 'ATT_NAME',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """Capitalization - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            small_camel (str): [optional]  # noqa: E501
+            capital_camel (str): [optional]  # noqa: E501
+            small_snake (str): [optional]  # noqa: E501
+            capital_snake (str): [optional]  # noqa: E501
+            sca_eth_flow_points (str): [optional]  # noqa: E501
+            att_name (str): Name of the pet . [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -179,3 +264,6 @@ class Capitalization(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent/petstore_api/model/cat.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.animal import Animal
@@ -98,6 +101,100 @@ class Cat(ModelComposed):
         'color': 'color',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """Cat - a model defined in OpenAPI
+
+        Keyword Args:
+            class_name (str):
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            declawed (bool): [optional]  # noqa: E501
+            color (str): [optional] if omitted the server will use the default value of "red"  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        constant_args = {
+            '_check_type': _check_type,
+            '_path_to_item': _path_to_item,
+            '_spec_property_naming': _spec_property_naming,
+            '_configuration': _configuration,
+            '_visited_composed_classes': self._visited_composed_classes,
+        }
+        composed_info = validate_get_composed_info(
+            constant_args, kwargs, self)
+        self._composed_instances = composed_info[0]
+        self._var_name_to_model_instances = composed_info[1]
+        self._additional_properties_model_instances = composed_info[2]
+        discarded_args = composed_info[3]
+
+        for var_name, var_value in kwargs.items():
+            if var_name in discarded_args and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self._additional_properties_model_instances:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -195,6 +292,9 @@ class Cat(ModelComposed):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")
 
     @cached_property
     def _composed_schemas():

samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent/petstore_api/model/cat_all_of.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class CatAllOf(ModelNormal):
@@ -84,8 +87,85 @@ class CatAllOf(ModelNormal):
         'declawed': 'declawed',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """CatAllOf - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            declawed (bool): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -164,3 +244,6 @@ class CatAllOf(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent/petstore_api/model/category.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class Category(ModelNormal):
@@ -86,8 +89,90 @@ class Category(ModelNormal):
         'id': 'id',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """Category - a model defined in OpenAPI
+
+        Args:
+
+        Keyword Args:
+            name (str): defaults to "default-name"  # noqa: E501
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            id (int): [optional]  # noqa: E501
+        """
+
+        name = kwargs.get('name', "default-name")
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        self.name = name
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -171,3 +256,6 @@ class Category(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent/petstore_api/model/child.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.child_all_of import ChildAllOf
@@ -95,6 +98,100 @@ class Child(ModelComposed):
         'inter_net': 'interNet',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """Child - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            radio_waves (bool): [optional]  # noqa: E501
+            tele_vision (bool): [optional]  # noqa: E501
+            inter_net (bool): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        constant_args = {
+            '_check_type': _check_type,
+            '_path_to_item': _path_to_item,
+            '_spec_property_naming': _spec_property_naming,
+            '_configuration': _configuration,
+            '_visited_composed_classes': self._visited_composed_classes,
+        }
+        composed_info = validate_get_composed_info(
+            constant_args, kwargs, self)
+        self._composed_instances = composed_info[0]
+        self._var_name_to_model_instances = composed_info[1]
+        self._additional_properties_model_instances = composed_info[2]
+        discarded_args = composed_info[3]
+
+        for var_name, var_value in kwargs.items():
+            if var_name in discarded_args and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self._additional_properties_model_instances:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -192,6 +289,9 @@ class Child(ModelComposed):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")
 
     @cached_property
     def _composed_schemas():

samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent/petstore_api/model/child_all_of.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 
 class ChildAllOf(ModelNormal):
@@ -84,8 +87,85 @@ class ChildAllOf(ModelNormal):
         'inter_net': 'interNet',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
     _composed_schemas = {}
 
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ChildAllOf - a model defined in OpenAPI
+
+        Keyword Args:
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            inter_net (bool): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        for var_name, var_value in kwargs.items():
+            if var_name not in self.attribute_map and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self.additional_properties_type is None:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -164,3 +244,6 @@ class ChildAllOf(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")

samples/client/petstore/python_disallowAdditionalPropertiesIfNotPresent/petstore_api/model/child_cat.py

@@ -25,6 +25,9 @@ from petstore_api.model_utils import (  # noqa: F401
     none_type,
     validate_get_composed_info,
 )
+from ..model_utils import OpenApiModel
+from petstore_api.exceptions import ApiAttributeError
+
 
 def lazy_import():
     from petstore_api.model.child_cat_all_of import ChildCatAllOf
@@ -96,6 +99,99 @@ class ChildCat(ModelComposed):
         'name': 'name',  # noqa: E501
     }
 
+    read_only_vars = {
+    }
+
+    @classmethod
+    @convert_js_args_to_python_args
+    def _from_openapi_data(cls, *args, **kwargs):  # noqa: E501
+        """ChildCat - a model defined in OpenAPI
+
+        Keyword Args:
+            pet_type (str):
+            _check_type (bool): if True, values for parameters in openapi_types
+                                will be type checked and a TypeError will be
+                                raised if the wrong type is input.
+                                Defaults to True
+            _path_to_item (tuple/list): This is a list of keys or values to
+                                drill down to the model in received_data
+                                when deserializing a response
+            _spec_property_naming (bool): True if the variable names in the input data
+                                are serialized names, as specified in the OpenAPI document.
+                                False if the variable names in the input data
+                                are pythonic names, e.g. snake case (default)
+            _configuration (Configuration): the instance to use when
+                                deserializing a file_type parameter.
+                                If passed, type conversion is attempted
+                                If omitted no type conversion is done.
+            _visited_composed_classes (tuple): This stores a tuple of
+                                classes that we have traveled through so that
+                                if we see that class again we will not use its
+                                discriminator again.
+                                When traveling through a discriminator, the
+                                composed schema that is
+                                is traveled through is added to this set.
+                                For example if Animal has a discriminator
+                                petType and we pass in "Dog", and the class Dog
+                                allOf includes Animal, we move through Animal
+                                once using the discriminator, and pick Dog.
+                                Then in Dog, we will make an instance of the
+                                Animal class but this time we won't travel
+                                through its discriminator because we passed in
+                                _visited_composed_classes = (Animal,)
+            name (str): [optional]  # noqa: E501
+        """
+
+        _check_type = kwargs.pop('_check_type', True)
+        _spec_property_naming = kwargs.pop('_spec_property_naming', False)
+        _path_to_item = kwargs.pop('_path_to_item', ())
+        _configuration = kwargs.pop('_configuration', None)
+        _visited_composed_classes = kwargs.pop('_visited_composed_classes', ())
+
+        self = super(OpenApiModel, cls).__new__(cls)
+
+        if args:
+            raise ApiTypeError(
+                "Invalid positional arguments=%s passed to %s. Remove those invalid positional arguments." % (
+                    args,
+                    self.__class__.__name__,
+                ),
+                path_to_item=_path_to_item,
+                valid_classes=(self.__class__,),
+            )
+
+        self._data_store = {}
+        self._check_type = _check_type
+        self._spec_property_naming = _spec_property_naming
+        self._path_to_item = _path_to_item
+        self._configuration = _configuration
+        self._visited_composed_classes = _visited_composed_classes + (self.__class__,)
+
+        constant_args = {
+            '_check_type': _check_type,
+            '_path_to_item': _path_to_item,
+            '_spec_property_naming': _spec_property_naming,
+            '_configuration': _configuration,
+            '_visited_composed_classes': self._visited_composed_classes,
+        }
+        composed_info = validate_get_composed_info(
+            constant_args, kwargs, self)
+        self._composed_instances = composed_info[0]
+        self._var_name_to_model_instances = composed_info[1]
+        self._additional_properties_model_instances = composed_info[2]
+        discarded_args = composed_info[3]
+
+        for var_name, var_value in kwargs.items():
+            if var_name in discarded_args and \
+                        self._configuration is not None and \
+                        self._configuration.discard_unknown_keys and \
+                        self._additional_properties_model_instances:
+                # discard variable.
+                continue
+            setattr(self, var_name, var_value)
+
+        return self
+
     required_properties = set([
         '_data_store',
         '_check_type',
@@ -192,6 +288,9 @@ class ChildCat(ModelComposed):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+            if var_name in self.read_only_vars:
+                raise ApiAttributeError(f"`{var_name}` is a read-only attribute. Use `from_openapi_data` to instantiate "
+                                     f"class with read only attributes.")
 
     @cached_property
     def _composed_schemas():