Add multiple servers support to Python client (#1969)

* add multiple server support to python client

* various fixes

* minor fixes, add tests

* test oas2 python first

* fix tests

* fix issues reported by flake8

* update code format

* add python petstore to ensure up-to-date

* rearrange test

* fix E501

* fix tests

* add new files

* fix script permission

* fix index check

* update samples

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

@@ -258,3 +258,54 @@ class Configuration(six.with_metaclass(TypeWithDefault, object)):
                "Version of the API: 1.0.0\n"\
                "SDK Package Version: 1.0.0".\
                format(env=sys.platform, pyversion=sys.version)
+
+    def get_host_settings(self):
+        """Gets an array of host settings
+
+        :return: An array of host settings
+        """
+        return [
+            {
+                'url': "http://petstore.swagger.io:80/v2",
+                'description': "No description provided",
+            }
+        ]
+
+    def get_host_from_settings(self, index, variables={}):
+        """Gets host URL based on the index and variables
+        :param index: array index of the host settings
+        :param variables: hash of variable and the corresponding value
+        :return: URL based on host settings
+        """
+
+        servers = self.get_host_settings()
+
+        # check array index out of bound
+        if index < 0 or index >= len(servers):
+            raise ValueError(
+                "Invalid index {} when selecting the host settings. Must be less than {}"  # noqa: E501
+                .format(index, len(servers)))
+
+        server = servers[index]
+        url = server['url']
+
+        # go through variable and assign a value
+        for variable_name in server['variables']:
+            if variable_name in variables:
+                if variables[variable_name] in server['variables'][
+                        variable_name]['enum_values']:
+                    url = url.replace("{" + variable_name + "}",
+                                      variables[variable_name])
+                else:
+                    raise ValueError(
+                        "The variable `{}` in the host URL has invalid value {}. Must be {}."  # noqa: E501
+                        .format(
+                            variable_name, variables[variable_name],
+                            server['variables'][variable_name]['enum_values']))
+            else:
+                # use default value
+                url = url.replace(
+                    "{" + variable_name + "}",
+                    server['variables'][variable_name]['default_value'])
+
+        return url