diff --git a/modules/swagger-codegen/src/main/resources/dart/api_client.mustache b/modules/swagger-codegen/src/main/resources/dart/api_client.mustache
index dcbd731d2af..86e698eb836 100644
--- a/modules/swagger-codegen/src/main/resources/dart/api_client.mustache
+++ b/modules/swagger-codegen/src/main/resources/dart/api_client.mustache
@@ -17,7 +17,6 @@ class ApiClient {
 
   final dson = new Dartson.JSON()
                    ..addTransformer(new DateTimeParser(), DateTime);
-  final DateFormat _dateFormatter = new DateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ");
 
   final _RegList = new RegExp(r'^List<(.*)>$');
   final _RegMap = new RegExp(r'^Map<String,(.*)>$');
@@ -33,24 +32,6 @@ class ApiClient {
      _defaultHeaderMap[key] = value;
   }
 
-  /// Format the given Date object into string.
-  String formatDate(DateTime date) {
-    return _dateFormatter.format(date);
-  }
-
-  /// Format the given parameter object into string.
-  String parameterToString(Object param) {
-    if (param == null) {
-      return '';
-    } else if (param is DateTime) {
-      return formatDate(param);
-    } else if (param is List) {
-      return (param).join(',');
-    } else {
-      return param.toString();
-    }
-  }
-
   dynamic _deserialize(dynamic value, String targetType) {
     try {
       switch (targetType) {
diff --git a/modules/swagger-codegen/src/main/resources/dart/api_helper.mustache b/modules/swagger-codegen/src/main/resources/dart/api_helper.mustache
index 6052dfb312b..15798ef3466 100644
--- a/modules/swagger-codegen/src/main/resources/dart/api_helper.mustache
+++ b/modules/swagger-codegen/src/main/resources/dart/api_helper.mustache
@@ -11,7 +11,7 @@ Iterable<QueryParam> _convertParametersForCollectionFormat(
   if (name == null || name.isEmpty || value == null) return params;
 
   if (value is! List) {
-    params.add(new QueryParam(name, '$value'));
+    params.add(new QueryParam(name, _parameterToString(value)));
     return params;
   }
 
@@ -23,11 +23,22 @@ Iterable<QueryParam> _convertParametersForCollectionFormat(
                      : collectionFormat; // default: csv
 
   if (collectionFormat == "multi") {
-    return values.map((v) => new QueryParam(name, '$v'));
+    return values.map((v) => new QueryParam(name, _parameterToString(v)));
   }
 
   String delimiter = _delimiters[collectionFormat] ?? ",";
 
-  params.add(new QueryParam(name, values.join(delimiter)));
+  params.add(new QueryParam(name, values.map((v)=>_parameterToString(v)).join(delimiter)));
   return params;
 }
+
+/// Format the given parameter object into string.
+String _parameterToString(dynamic value) {
+  if (value == null) {
+    return '';
+  } else if (value is DateTime) {
+    return value.toUtc().toIso8601String();
+  } else {
+    return value.toString();
+  }
+}
\ No newline at end of file
diff --git a/modules/swagger-codegen/src/main/resources/dart/apilib.mustache b/modules/swagger-codegen/src/main/resources/dart/apilib.mustache
index 07b02ef6105..8f131054f25 100644
--- a/modules/swagger-codegen/src/main/resources/dart/apilib.mustache
+++ b/modules/swagger-codegen/src/main/resources/dart/apilib.mustache
@@ -6,7 +6,6 @@ import 'package:http/browser_client.dart';{{/browserClient}}
 import 'package:http/http.dart';
 import 'package:dartson/dartson.dart';
 import 'package:dartson/transformers/date_time.dart';
-import 'package:intl/intl.dart';
 
 part 'api_client.dart';
 part 'api_helper.dart';
diff --git a/modules/swagger-codegen/src/main/resources/dart/pubspec.mustache b/modules/swagger-codegen/src/main/resources/dart/pubspec.mustache
index ce0a309ea82..5a580b2696d 100644
--- a/modules/swagger-codegen/src/main/resources/dart/pubspec.mustache
+++ b/modules/swagger-codegen/src/main/resources/dart/pubspec.mustache
@@ -4,7 +4,6 @@ description: {{pubDescription}}
 dependencies:
   http: '>=0.11.1 <0.12.0'
   dartson: "^0.2.4"
-  intl: ">=0.12.4"
 
 dev_dependencies:
   guinness: '^0.1.17'
diff --git a/modules/swagger-codegen/src/main/resources/python/api.mustache b/modules/swagger-codegen/src/main/resources/python/api.mustache
index 2d86c9de66c..c6a07b2f7a2 100644
--- a/modules/swagger-codegen/src/main/resources/python/api.mustache
+++ b/modules/swagger-codegen/src/main/resources/python/api.mustache
@@ -98,6 +98,7 @@ class {{classname}}(object):
         all_params = [{{#allParams}}'{{paramName}}'{{#hasMore}}, {{/hasMore}}{{/allParams}}]
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -211,6 +212,7 @@ class {{classname}}(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
 {{/operation}}
 {{/operations}}
diff --git a/modules/swagger-codegen/src/main/resources/python/api_client.mustache b/modules/swagger-codegen/src/main/resources/python/api_client.mustache
index dc4fe509f62..11646705495 100644
--- a/modules/swagger-codegen/src/main/resources/python/api_client.mustache
+++ b/modules/swagger-codegen/src/main/resources/python/api_client.mustache
@@ -96,7 +96,7 @@ class ApiClient(object):
                    path_params=None, query_params=None, header_params=None,
                    body=None, post_params=None, files=None,
                    response_type=None, auth_settings=None, callback=None,
-                   _return_http_data_only=None, collection_formats=None):
+                   _return_http_data_only=None, collection_formats=None, _preload_content=True):
 
         # header parameters
         header_params = header_params or {}
@@ -144,22 +144,24 @@ class ApiClient(object):
         response_data = self.request(method, url,
                                      query_params=query_params,
                                      headers=header_params,
-                                     post_params=post_params, body=body)
+                                     post_params=post_params, body=body, _preload_content=_preload_content)
 
         self.last_response = response_data
 
-        # deserialize response data
-        if response_type:
-            deserialized_data = self.deserialize(response_data, response_type)
-        else:
-            deserialized_data = None
+        return_data = response_data
+        if _preload_content:
+            # deserialize response data
+            if response_type:
+                return_data = self.deserialize(response_data, response_type)
+            else:
+                return_data = None
 
         if callback:
-            callback(deserialized_data) if _return_http_data_only else callback((deserialized_data, response_data.status, response_data.getheaders()))
+            callback(return_data) if _return_http_data_only else callback((return_data, response_data.status, response_data.getheaders()))
         elif _return_http_data_only:
-            return (deserialized_data)
+            return (return_data)
         else:
-            return (deserialized_data, response_data.status, response_data.getheaders())
+            return (return_data, response_data.status, response_data.getheaders())
 
     def sanitize_for_serialization(self, obj):
         """
@@ -277,7 +279,7 @@ class ApiClient(object):
                  path_params=None, query_params=None, header_params=None,
                  body=None, post_params=None, files=None,
                  response_type=None, auth_settings=None, callback=None,
-                 _return_http_data_only=None, collection_formats=None):
+                 _return_http_data_only=None, collection_formats=None, _preload_content=True):
         """
         Makes the HTTP request (synchronous) and return the deserialized data.
         To make an async request, define a function for callback.
@@ -307,13 +309,15 @@ class ApiClient(object):
             The method will return the request thread.
             If parameter callback is None,
             then the method will return the response directly.
+        :param _preload_content: if False, the urllib3.HTTPResponse object will be returned without
+                                 reading/decoding response data. Default is True.
         """
         if callback is None:
             return self.__call_api(resource_path, method,
                                    path_params, query_params, header_params,
                                    body, post_params, files,
                                    response_type, auth_settings, callback,
-                                   _return_http_data_only, collection_formats)
+                                   _return_http_data_only, collection_formats, _preload_content)
         else:
             thread = threading.Thread(target=self.__call_api,
                                       args=(resource_path, method,
@@ -322,51 +326,58 @@ class ApiClient(object):
                                             post_params, files,
                                             response_type, auth_settings,
                                             callback, _return_http_data_only,
-                                            collection_formats))
+                                            collection_formats, _preload_content))
         thread.start()
         return thread
 
     def request(self, method, url, query_params=None, headers=None,
-                post_params=None, body=None):
+                post_params=None, body=None, _preload_content=True):
         """
         Makes the HTTP request using RESTClient.
         """
         if method == "GET":
             return self.rest_client.GET(url,
                                         query_params=query_params,
+                                        _preload_content=_preload_content,
                                         headers=headers)
         elif method == "HEAD":
             return self.rest_client.HEAD(url,
                                          query_params=query_params,
+                                         _preload_content=_preload_content,
                                          headers=headers)
         elif method == "OPTIONS":
             return self.rest_client.OPTIONS(url,
                                             query_params=query_params,
                                             headers=headers,
                                             post_params=post_params,
+                                            _preload_content=_preload_content,
                                             body=body)
         elif method == "POST":
             return self.rest_client.POST(url,
                                          query_params=query_params,
                                          headers=headers,
                                          post_params=post_params,
+                                         _preload_content=_preload_content,
                                          body=body)
         elif method == "PUT":
             return self.rest_client.PUT(url,
                                         query_params=query_params,
                                         headers=headers,
                                         post_params=post_params,
+                                        _preload_content=_preload_content,
                                         body=body)
         elif method == "PATCH":
             return self.rest_client.PATCH(url,
                                           query_params=query_params,
                                           headers=headers,
                                           post_params=post_params,
+                                          _preload_content=_preload_content,
                                           body=body)
         elif method == "DELETE":
             return self.rest_client.DELETE(url,
                                            query_params=query_params,
                                            headers=headers,
+                                           _preload_content=_preload_content,
                                            body=body)
         else:
             raise ValueError(
diff --git a/modules/swagger-codegen/src/main/resources/python/rest.mustache b/modules/swagger-codegen/src/main/resources/python/rest.mustache
index 9bdddc91904..3f0e3dca292 100644
--- a/modules/swagger-codegen/src/main/resources/python/rest.mustache
+++ b/modules/swagger-codegen/src/main/resources/python/rest.mustache
@@ -85,7 +85,7 @@ class RESTClientObject(object):
         )
 
     def request(self, method, url, query_params=None, headers=None,
-                body=None, post_params=None):
+                body=None, post_params=None, _preload_content=True):
         """
         :param method: http request method
         :param url: http request url
@@ -95,6 +95,8 @@ class RESTClientObject(object):
         :param post_params: request post parameters,
                             `application/x-www-form-urlencoded`
                             and `multipart/form-data`
+        :param _preload_content: if False, the urllib3.HTTPResponse object will be returned without
+                                 reading/decoding response data. Default is True.
         """
         method = method.upper()
         assert method in ['GET', 'HEAD', 'DELETE', 'POST', 'PUT', 'PATCH', 'OPTIONS']
@@ -121,11 +123,13 @@ class RESTClientObject(object):
                         request_body = json.dumps(body)
                     r = self.pool_manager.request(method, url,
                                                   body=request_body,
+                                                  preload_content=_preload_content,
                                                   headers=headers)
                 elif headers['Content-Type'] == 'application/x-www-form-urlencoded':
                     r = self.pool_manager.request(method, url,
                                                   fields=post_params,
                                                   encode_multipart=False,
+                                                  preload_content=_preload_content,
                                                   headers=headers)
                 elif headers['Content-Type'] == 'multipart/form-data':
                     # must del headers['Content-Type'], or the correct Content-Type
@@ -134,6 +138,7 @@ class RESTClientObject(object):
                     r = self.pool_manager.request(method, url,
                                                   fields=post_params,
                                                   encode_multipart=True,
+                                                  preload_content=_preload_content,
                                                   headers=headers)
                 # Pass a `string` parameter directly in the body to support
                 # other content types than Json when `body` argument is provided
@@ -142,6 +147,7 @@ class RESTClientObject(object):
                     request_body = body
                     r = self.pool_manager.request(method, url,
                                                   body=request_body,
+                                                  preload_content=_preload_content,
                                                   headers=headers)
                 else:
                     # Cannot generate the request from given parameters
@@ -152,68 +158,77 @@ class RESTClientObject(object):
             else:
                 r = self.pool_manager.request(method, url,
                                               fields=query_params,
+                                              preload_content=_preload_content,
                                               headers=headers)
         except urllib3.exceptions.SSLError as e:
             msg = "{0}\n{1}".format(type(e).__name__, str(e))
             raise ApiException(status=0, reason=msg)
 
-        r = RESTResponse(r)
+        if _preload_content:
+            r = RESTResponse(r)
 
-        # In the python 3, the response.data is bytes.
-        # we need to decode it to string.
-        if PY3:
-            r.data = r.data.decode('utf8')
+            # In the python 3, the response.data is bytes.
+            # we need to decode it to string.
+            if PY3:
+                r.data = r.data.decode('utf8')
 
-        # log response body
-        logger.debug("response body: %s", r.data)
+            # log response body
+            logger.debug("response body: %s", r.data)
 
         if r.status not in range(200, 206):
             raise ApiException(http_resp=r)
 
         return r
 
-    def GET(self, url, headers=None, query_params=None):
+    def GET(self, url, headers=None, query_params=None, _preload_content=True):
         return self.request("GET", url,
                             headers=headers,
+                            _preload_content=_preload_content,
                             query_params=query_params)
 
-    def HEAD(self, url, headers=None, query_params=None):
+    def HEAD(self, url, headers=None, query_params=None, _preload_content=True):
         return self.request("HEAD", url,
                             headers=headers,
+                            _preload_content=_preload_content,
                             query_params=query_params)
 
-    def OPTIONS(self, url, headers=None, query_params=None, post_params=None, body=None):
+    def OPTIONS(self, url, headers=None, query_params=None, post_params=None, body=None, _preload_content=True):
         return self.request("OPTIONS", url,
                             headers=headers,
                             query_params=query_params,
                             post_params=post_params,
+                            _preload_content=_preload_content,
                             body=body)
 
-    def DELETE(self, url, headers=None, query_params=None, body=None):
+    def DELETE(self, url, headers=None, query_params=None, body=None, _preload_content=True):
         return self.request("DELETE", url,
                             headers=headers,
                             query_params=query_params,
+                            _preload_content=_preload_content,
                             body=body)
 
-    def POST(self, url, headers=None, query_params=None, post_params=None, body=None):
+    def POST(self, url, headers=None, query_params=None, post_params=None, body=None, _preload_content=True):
         return self.request("POST", url,
                             headers=headers,
                             query_params=query_params,
                             post_params=post_params,
+                            _preload_content=_preload_content,
                             body=body)
 
-    def PUT(self, url, headers=None, query_params=None, post_params=None, body=None):
+    def PUT(self, url, headers=None, query_params=None, post_params=None, body=None, _preload_content=True):
         return self.request("PUT", url,
                             headers=headers,
                             query_params=query_params,
                             post_params=post_params,
+                            _preload_content=_preload_content,
                             body=body)
 
-    def PATCH(self, url, headers=None, query_params=None, post_params=None, body=None):
+    def PATCH(self, url, headers=None, query_params=None, post_params=None, body=None, _preload_content=True):
         return self.request("PATCH", url,
                             headers=headers,
                             query_params=query_params,
                             post_params=post_params,
+                            _preload_content=_preload_content,
                             body=body)
 
 
diff --git a/samples/client/petstore/dart/swagger/lib/api.dart b/samples/client/petstore/dart/swagger/lib/api.dart
index db95000d614..9273d7f1f99 100644
--- a/samples/client/petstore/dart/swagger/lib/api.dart
+++ b/samples/client/petstore/dart/swagger/lib/api.dart
@@ -6,7 +6,6 @@ import 'package:http/browser_client.dart';
 import 'package:http/http.dart';
 import 'package:dartson/dartson.dart';
 import 'package:dartson/transformers/date_time.dart';
-import 'package:intl/intl.dart';
 
 part 'api_client.dart';
 part 'api_helper.dart';
diff --git a/samples/client/petstore/dart/swagger/lib/api_client.dart b/samples/client/petstore/dart/swagger/lib/api_client.dart
index 73856b69d74..9552cef10d8 100644
--- a/samples/client/petstore/dart/swagger/lib/api_client.dart
+++ b/samples/client/petstore/dart/swagger/lib/api_client.dart
@@ -17,7 +17,6 @@ class ApiClient {
 
   final dson = new Dartson.JSON()
                    ..addTransformer(new DateTimeParser(), DateTime);
-  final DateFormat _dateFormatter = new DateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ");
 
   final _RegList = new RegExp(r'^List<(.*)>$');
   final _RegMap = new RegExp(r'^Map<String,(.*)>$');
@@ -32,24 +31,6 @@ class ApiClient {
      _defaultHeaderMap[key] = value;
   }
 
-  /// Format the given Date object into string.
-  String formatDate(DateTime date) {
-    return _dateFormatter.format(date);
-  }
-
-  /// Format the given parameter object into string.
-  String parameterToString(Object param) {
-    if (param == null) {
-      return '';
-    } else if (param is DateTime) {
-      return formatDate(param);
-    } else if (param is List) {
-      return (param).join(',');
-    } else {
-      return param.toString();
-    }
-  }
-
   dynamic _deserialize(dynamic value, String targetType) {
     try {
       switch (targetType) {
diff --git a/samples/client/petstore/dart/swagger/lib/api_helper.dart b/samples/client/petstore/dart/swagger/lib/api_helper.dart
index ad73218ab40..7d2c3471a9f 100644
--- a/samples/client/petstore/dart/swagger/lib/api_helper.dart
+++ b/samples/client/petstore/dart/swagger/lib/api_helper.dart
@@ -11,7 +11,7 @@ Iterable<QueryParam> _convertParametersForCollectionFormat(
   if (name == null || name.isEmpty || value == null) return params;
 
   if (value is! List) {
-    params.add(new QueryParam(name, '$value'));
+    params.add(new QueryParam(name, _parameterToString(value)));
     return params;
   }
 
@@ -23,11 +23,22 @@ Iterable<QueryParam> _convertParametersForCollectionFormat(
                      : collectionFormat; // default: csv
 
   if (collectionFormat == "multi") {
-    return values.map((v) => new QueryParam(name, '$v'));
+    return values.map((v) => new QueryParam(name, _parameterToString(v)));
   }
 
   String delimiter = _delimiters[collectionFormat] ?? ",";
 
-  params.add(new QueryParam(name, values.join(delimiter)));
+  params.add(new QueryParam(name, values.map((v)=>_parameterToString(v)).join(delimiter)));
   return params;
 }
+
+/// Format the given parameter object into string.
+String _parameterToString(dynamic value) {
+  if (value == null) {
+    return '';
+  } else if (value is DateTime) {
+    return value.toUtc().toIso8601String();
+  } else {
+    return value.toString();
+  }
+}
\ No newline at end of file
diff --git a/samples/client/petstore/dart/swagger/pubspec.yaml b/samples/client/petstore/dart/swagger/pubspec.yaml
index 8ad53b9d6e6..50938a1c095 100644
--- a/samples/client/petstore/dart/swagger/pubspec.yaml
+++ b/samples/client/petstore/dart/swagger/pubspec.yaml
@@ -4,7 +4,6 @@ description: Swagger API client
 dependencies:
   http: '>=0.11.1 <0.12.0'
   dartson: "^0.2.4"
-  intl: ">=0.12.4"
 
 dev_dependencies:
   guinness: '^0.1.17'
diff --git a/samples/client/petstore/python/docs/FakeApi.md b/samples/client/petstore/python/docs/FakeApi.md
index c6ed3ccfbfc..69186f43a50 100644
--- a/samples/client/petstore/python/docs/FakeApi.md
+++ b/samples/client/petstore/python/docs/FakeApi.md
@@ -186,8 +186,8 @@ No authorization required
 
 ### HTTP request headers
 
- - **Content-Type**: application/json
- - **Accept**: application/json
+ - **Content-Type**: */*
+ - **Accept**: */*
 
 [[Back to top]](#) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to Model list]](../README.md#documentation-for-models) [[Back to README]](../README.md)
 
diff --git a/samples/client/petstore/python/petstore_api/api_client.py b/samples/client/petstore/python/petstore_api/api_client.py
index bd57c1089a4..f13cb3772ad 100644
--- a/samples/client/petstore/python/petstore_api/api_client.py
+++ b/samples/client/petstore/python/petstore_api/api_client.py
@@ -96,7 +96,7 @@ class ApiClient(object):
                    path_params=None, query_params=None, header_params=None,
                    body=None, post_params=None, files=None,
                    response_type=None, auth_settings=None, callback=None,
-                   _return_http_data_only=None, collection_formats=None):
+                   _return_http_data_only=None, collection_formats=None, _preload_content=True):
 
         # header parameters
         header_params = header_params or {}
@@ -144,22 +144,24 @@ class ApiClient(object):
         response_data = self.request(method, url,
                                      query_params=query_params,
                                      headers=header_params,
-                                     post_params=post_params, body=body)
+                                     post_params=post_params, body=body, _preload_content=_preload_content)
 
         self.last_response = response_data
 
-        # deserialize response data
-        if response_type:
-            deserialized_data = self.deserialize(response_data, response_type)
-        else:
-            deserialized_data = None
+        return_data = response_data
+        if _preload_content:
+            # deserialize response data
+            if response_type:
+                return_data = self.deserialize(response_data, response_type)
+            else:
+                return_data = None
 
         if callback:
-            callback(deserialized_data) if _return_http_data_only else callback((deserialized_data, response_data.status, response_data.getheaders()))
+            callback(return_data) if _return_http_data_only else callback((return_data, response_data.status, response_data.getheaders()))
         elif _return_http_data_only:
-            return (deserialized_data)
+            return (return_data)
         else:
-            return (deserialized_data, response_data.status, response_data.getheaders())
+            return (return_data, response_data.status, response_data.getheaders())
 
     def sanitize_for_serialization(self, obj):
         """
@@ -277,7 +279,7 @@ class ApiClient(object):
                  path_params=None, query_params=None, header_params=None,
                  body=None, post_params=None, files=None,
                  response_type=None, auth_settings=None, callback=None,
-                 _return_http_data_only=None, collection_formats=None):
+                 _return_http_data_only=None, collection_formats=None, _preload_content=True):
         """
         Makes the HTTP request (synchronous) and return the deserialized data.
         To make an async request, define a function for callback.
@@ -307,13 +309,15 @@ class ApiClient(object):
             The method will return the request thread.
             If parameter callback is None,
             then the method will return the response directly.
+        :param _preload_content: if False, the urllib3.HTTPResponse object will be returned without
+                                 reading/decoding response data. Default is True.
         """
         if callback is None:
             return self.__call_api(resource_path, method,
                                    path_params, query_params, header_params,
                                    body, post_params, files,
                                    response_type, auth_settings, callback,
-                                   _return_http_data_only, collection_formats)
+                                   _return_http_data_only, collection_formats, _preload_content)
         else:
             thread = threading.Thread(target=self.__call_api,
                                       args=(resource_path, method,
@@ -322,51 +326,58 @@ class ApiClient(object):
                                             post_params, files,
                                             response_type, auth_settings,
                                             callback, _return_http_data_only,
-                                            collection_formats))
+                                            collection_formats, _preload_content))
         thread.start()
         return thread
 
     def request(self, method, url, query_params=None, headers=None,
-                post_params=None, body=None):
+                post_params=None, body=None, _preload_content=True):
         """
         Makes the HTTP request using RESTClient.
         """
         if method == "GET":
             return self.rest_client.GET(url,
                                         query_params=query_params,
+                                        _preload_content=_preload_content,
                                         headers=headers)
         elif method == "HEAD":
             return self.rest_client.HEAD(url,
                                          query_params=query_params,
+                                         _preload_content=_preload_content,
                                          headers=headers)
         elif method == "OPTIONS":
             return self.rest_client.OPTIONS(url,
                                             query_params=query_params,
                                             headers=headers,
                                             post_params=post_params,
+                                            _preload_content=_preload_content,
                                             body=body)
         elif method == "POST":
             return self.rest_client.POST(url,
                                          query_params=query_params,
                                          headers=headers,
                                          post_params=post_params,
+                                         _preload_content=_preload_content,
                                          body=body)
         elif method == "PUT":
             return self.rest_client.PUT(url,
                                         query_params=query_params,
                                         headers=headers,
                                         post_params=post_params,
+                                        _preload_content=_preload_content,
                                         body=body)
         elif method == "PATCH":
             return self.rest_client.PATCH(url,
                                           query_params=query_params,
                                           headers=headers,
                                           post_params=post_params,
+                                          _preload_content=_preload_content,
                                           body=body)
         elif method == "DELETE":
             return self.rest_client.DELETE(url,
                                            query_params=query_params,
                                            headers=headers,
+                                           _preload_content=_preload_content,
                                            body=body)
         else:
             raise ValueError(
diff --git a/samples/client/petstore/python/petstore_api/apis/fake_api.py b/samples/client/petstore/python/petstore_api/apis/fake_api.py
index 944396a9fdc..cdf79483bc9 100644
--- a/samples/client/petstore/python/petstore_api/apis/fake_api.py
+++ b/samples/client/petstore/python/petstore_api/apis/fake_api.py
@@ -102,6 +102,7 @@ class FakeApi(object):
         all_params = ['body']
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -157,6 +158,7 @@ class FakeApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
 
     def test_endpoint_parameters(self, number, double, pattern_without_delimiter, byte, **kwargs):
@@ -236,6 +238,7 @@ class FakeApi(object):
         all_params = ['number', 'double', 'pattern_without_delimiter', 'byte', 'integer', 'int32', 'int64', 'float', 'string', 'binary', 'date', 'date_time', 'password', 'param_callback']
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -352,6 +355,7 @@ class FakeApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
 
     def test_enum_parameters(self, **kwargs):
@@ -419,6 +423,7 @@ class FakeApi(object):
         all_params = ['enum_form_string_array', 'enum_form_string', 'enum_header_string_array', 'enum_header_string', 'enum_query_string_array', 'enum_query_string', 'enum_query_integer', 'enum_query_double']
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -466,13 +471,13 @@ class FakeApi(object):
 
         # HTTP header `Accept`
         header_params['Accept'] = self.api_client.\
-            select_header_accept(['application/json'])
+            select_header_accept(['*/*'])
         if not header_params['Accept']:
             del header_params['Accept']
 
         # HTTP header `Content-Type`
         header_params['Content-Type'] = self.api_client.\
-            select_header_content_type(['application/json'])
+            select_header_content_type(['*/*'])
 
         # Authentication setting
         auth_settings = []
@@ -488,4 +493,5 @@ class FakeApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
diff --git a/samples/client/petstore/python/petstore_api/apis/pet_api.py b/samples/client/petstore/python/petstore_api/apis/pet_api.py
index b0aa2d9a842..d8c5eefc946 100644
--- a/samples/client/petstore/python/petstore_api/apis/pet_api.py
+++ b/samples/client/petstore/python/petstore_api/apis/pet_api.py
@@ -102,6 +102,7 @@ class PetApi(object):
         all_params = ['body']
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -157,6 +158,7 @@ class PetApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
 
     def delete_pet(self, pet_id, **kwargs):
@@ -212,6 +214,7 @@ class PetApi(object):
         all_params = ['pet_id', 'api_key']
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -269,6 +272,7 @@ class PetApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
 
     def find_pets_by_status(self, status, **kwargs):
@@ -322,6 +326,7 @@ class PetApi(object):
         all_params = ['status']
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -378,6 +383,7 @@ class PetApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
 
     def find_pets_by_tags(self, tags, **kwargs):
@@ -431,6 +437,7 @@ class PetApi(object):
         all_params = ['tags']
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -487,6 +494,7 @@ class PetApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
 
     def get_pet_by_id(self, pet_id, **kwargs):
@@ -540,6 +548,7 @@ class PetApi(object):
         all_params = ['pet_id']
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -595,6 +604,7 @@ class PetApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
 
     def update_pet(self, body, **kwargs):
@@ -648,6 +658,7 @@ class PetApi(object):
         all_params = ['body']
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -703,6 +714,7 @@ class PetApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
 
     def update_pet_with_form(self, pet_id, **kwargs):
@@ -760,6 +772,7 @@ class PetApi(object):
         all_params = ['pet_id', 'name', 'status']
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -819,6 +832,7 @@ class PetApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
 
     def upload_file(self, pet_id, **kwargs):
@@ -876,6 +890,7 @@ class PetApi(object):
         all_params = ['pet_id', 'additional_metadata', 'file']
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -935,4 +950,5 @@ class PetApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
diff --git a/samples/client/petstore/python/petstore_api/apis/store_api.py b/samples/client/petstore/python/petstore_api/apis/store_api.py
index c7f37de09e8..adcf8d2b4ed 100644
--- a/samples/client/petstore/python/petstore_api/apis/store_api.py
+++ b/samples/client/petstore/python/petstore_api/apis/store_api.py
@@ -102,6 +102,7 @@ class StoreApi(object):
         all_params = ['order_id']
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -159,6 +160,7 @@ class StoreApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
 
     def get_inventory(self, **kwargs):
@@ -210,6 +212,7 @@ class StoreApi(object):
         all_params = []
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -260,6 +263,7 @@ class StoreApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
 
     def get_order_by_id(self, order_id, **kwargs):
@@ -313,6 +317,7 @@ class StoreApi(object):
         all_params = ['order_id']
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -372,6 +377,7 @@ class StoreApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
 
     def place_order(self, body, **kwargs):
@@ -425,6 +431,7 @@ class StoreApi(object):
         all_params = ['body']
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -480,4 +487,5 @@ class StoreApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
diff --git a/samples/client/petstore/python/petstore_api/apis/user_api.py b/samples/client/petstore/python/petstore_api/apis/user_api.py
index cc7f2d35083..255b68a8c7f 100644
--- a/samples/client/petstore/python/petstore_api/apis/user_api.py
+++ b/samples/client/petstore/python/petstore_api/apis/user_api.py
@@ -102,6 +102,7 @@ class UserApi(object):
         all_params = ['body']
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -157,6 +158,7 @@ class UserApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
 
     def create_users_with_array_input(self, body, **kwargs):
@@ -210,6 +212,7 @@ class UserApi(object):
         all_params = ['body']
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -265,6 +268,7 @@ class UserApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
 
     def create_users_with_list_input(self, body, **kwargs):
@@ -318,6 +322,7 @@ class UserApi(object):
         all_params = ['body']
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -373,6 +378,7 @@ class UserApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
 
     def delete_user(self, username, **kwargs):
@@ -426,6 +432,7 @@ class UserApi(object):
         all_params = ['username']
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -481,6 +488,7 @@ class UserApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
 
     def get_user_by_name(self, username, **kwargs):
@@ -534,6 +542,7 @@ class UserApi(object):
         all_params = ['username']
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -589,6 +598,7 @@ class UserApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
 
     def login_user(self, username, password, **kwargs):
@@ -644,6 +654,7 @@ class UserApi(object):
         all_params = ['username', 'password']
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -704,6 +715,7 @@ class UserApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
 
     def logout_user(self, **kwargs):
@@ -755,6 +767,7 @@ class UserApi(object):
         all_params = []
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -805,6 +818,7 @@ class UserApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
 
     def update_user(self, username, body, **kwargs):
@@ -860,6 +874,7 @@ class UserApi(object):
         all_params = ['username', 'body']
         all_params.append('callback')
         all_params.append('_return_http_data_only')
+        all_params.append('_preload_content')
 
         params = locals()
         for key, val in iteritems(params['kwargs']):
@@ -920,4 +935,5 @@ class UserApi(object):
                                             auth_settings=auth_settings,
                                             callback=params.get('callback'),
                                             _return_http_data_only=params.get('_return_http_data_only'),
+                                            _preload_content=params.get('_preload_content', True),
                                             collection_formats=collection_formats)
diff --git a/samples/client/petstore/python/petstore_api/rest.py b/samples/client/petstore/python/petstore_api/rest.py
index f8a4457ebae..c61b29c8120 100644
--- a/samples/client/petstore/python/petstore_api/rest.py
+++ b/samples/client/petstore/python/petstore_api/rest.py
@@ -105,7 +105,7 @@ class RESTClientObject(object):
         )
 
     def request(self, method, url, query_params=None, headers=None,
-                body=None, post_params=None):
+                body=None, post_params=None, _preload_content=True):
         """
         :param method: http request method
         :param url: http request url
@@ -115,6 +115,8 @@ class RESTClientObject(object):
         :param post_params: request post parameters,
                             `application/x-www-form-urlencoded`
                             and `multipart/form-data`
+        :param _preload_content: if False, the urllib3.HTTPResponse object will be returned without
+                                 reading/decoding response data. Default is True.
         """
         method = method.upper()
         assert method in ['GET', 'HEAD', 'DELETE', 'POST', 'PUT', 'PATCH', 'OPTIONS']
@@ -141,11 +143,13 @@ class RESTClientObject(object):
                         request_body = json.dumps(body)
                     r = self.pool_manager.request(method, url,
                                                   body=request_body,
+                                                  preload_content=_preload_content,
                                                   headers=headers)
                 elif headers['Content-Type'] == 'application/x-www-form-urlencoded':
                     r = self.pool_manager.request(method, url,
                                                   fields=post_params,
                                                   encode_multipart=False,
+                                                  preload_content=_preload_content,
                                                   headers=headers)
                 elif headers['Content-Type'] == 'multipart/form-data':
                     # must del headers['Content-Type'], or the correct Content-Type
@@ -154,6 +158,7 @@ class RESTClientObject(object):
                     r = self.pool_manager.request(method, url,
                                                   fields=post_params,
                                                   encode_multipart=True,
+                                                  preload_content=_preload_content,
                                                   headers=headers)
                 # Pass a `string` parameter directly in the body to support
                 # other content types than Json when `body` argument is provided
@@ -162,6 +167,7 @@ class RESTClientObject(object):
                     request_body = body
                     r = self.pool_manager.request(method, url,
                                                   body=request_body,
+                                                  preload_content=_preload_content,
                                                   headers=headers)
                 else:
                     # Cannot generate the request from given parameters
@@ -172,68 +178,77 @@ class RESTClientObject(object):
             else:
                 r = self.pool_manager.request(method, url,
                                               fields=query_params,
+                                              preload_content=_preload_content,
                                               headers=headers)
         except urllib3.exceptions.SSLError as e:
             msg = "{0}\n{1}".format(type(e).__name__, str(e))
             raise ApiException(status=0, reason=msg)
 
-        r = RESTResponse(r)
+        if _preload_content:
+            r = RESTResponse(r)
 
-        # In the python 3, the response.data is bytes.
-        # we need to decode it to string.
-        if PY3:
-            r.data = r.data.decode('utf8')
+            # In the python 3, the response.data is bytes.
+            # we need to decode it to string.
+            if PY3:
+                r.data = r.data.decode('utf8')
 
-        # log response body
-        logger.debug("response body: %s", r.data)
+            # log response body
+            logger.debug("response body: %s", r.data)
 
         if r.status not in range(200, 206):
             raise ApiException(http_resp=r)
 
         return r
 
-    def GET(self, url, headers=None, query_params=None):
+    def GET(self, url, headers=None, query_params=None, _preload_content=True):
         return self.request("GET", url,
                             headers=headers,
+                            _preload_content=_preload_content,
                             query_params=query_params)
 
-    def HEAD(self, url, headers=None, query_params=None):
+    def HEAD(self, url, headers=None, query_params=None, _preload_content=True):
         return self.request("HEAD", url,
                             headers=headers,
+                            _preload_content=_preload_content,
                             query_params=query_params)
 
-    def OPTIONS(self, url, headers=None, query_params=None, post_params=None, body=None):
+    def OPTIONS(self, url, headers=None, query_params=None, post_params=None, body=None, _preload_content=True):
         return self.request("OPTIONS", url,
                             headers=headers,
                             query_params=query_params,
                             post_params=post_params,
+                            _preload_content=_preload_content,
                             body=body)
 
-    def DELETE(self, url, headers=None, query_params=None, body=None):
+    def DELETE(self, url, headers=None, query_params=None, body=None, _preload_content=True):
         return self.request("DELETE", url,
                             headers=headers,
                             query_params=query_params,
+                            _preload_content=_preload_content,
                             body=body)
 
-    def POST(self, url, headers=None, query_params=None, post_params=None, body=None):
+    def POST(self, url, headers=None, query_params=None, post_params=None, body=None, _preload_content=True):
         return self.request("POST", url,
                             headers=headers,
                             query_params=query_params,
                             post_params=post_params,
+                            _preload_content=_preload_content,
                             body=body)
 
-    def PUT(self, url, headers=None, query_params=None, post_params=None, body=None):
+    def PUT(self, url, headers=None, query_params=None, post_params=None, body=None, _preload_content=True):
         return self.request("PUT", url,
                             headers=headers,
                             query_params=query_params,
                             post_params=post_params,
+                            _preload_content=_preload_content,
                             body=body)
 
-    def PATCH(self, url, headers=None, query_params=None, post_params=None, body=None):
+    def PATCH(self, url, headers=None, query_params=None, post_params=None, body=None, _preload_content=True):
         return self.request("PATCH", url,
                             headers=headers,
                             query_params=query_params,
                             post_params=post_params,
+                            _preload_content=_preload_content,
                             body=body)