diff --git a/modules/openapi-generator/src/main/resources/python/rest.mustache b/modules/openapi-generator/src/main/resources/python/rest.mustache
index 5d852b28d92b..f814e2334575 100644
--- a/modules/openapi-generator/src/main/resources/python/rest.mustache
+++ b/modules/openapi-generator/src/main/resources/python/rest.mustache
@@ -27,6 +27,21 @@ def is_socks_proxy_url(url):
     else:
         return split_section[0].lower() in SUPPORTED_SOCKS_PROXIES
 
+def contenttype_matches(contenttype, maintype, subtype):
+    """Matches the given contenttype against the given type and subtype
+
+    :param contenttype: the content type to match
+    :param maintype: the expected maintype
+    :param subtype: the expected subtype
+    :return: `true` when the given content type matches the given type and subtype,
+        regardless of the presence of mime type parameters, otherwise returns `false`.
+    :rtype: bool
+    """
+    pattern = '{type}/(?:[^+;]+\\+)?{subtype}(?:[ \t]*;.*)?'.format(
+        type = re.escape(maintype),
+        subtype = re.escape(subtype),
+    )
+    return re.fullmatch(pattern, contenttype, re.IGNORECASE) is not None
 
 def should_bypass_proxies(url: str, no_proxy: str) -> bool:
     """Return whether ``url`` matches the comma-separated ``no_proxy`` rules."""
@@ -212,14 +227,18 @@ class RESTClientObject:
                 content_type = headers.get('Content-Type')
                 is_json = (
                     not content_type
-                    or re.search('json', content_type, re.IGNORECASE)
+                    or contenttype_matches(content_type, 'application', 'json')
                 )
                 # JSON is valid YAML 1.2, so structured YAML bodies can use
                 # the existing JSON serializer:
                 # https://yaml.org/spec/1.2.2/#13-relation-to-json
                 is_structured_yaml = (
                     content_type
-                    and re.search('yaml', content_type, re.IGNORECASE)
+                    and (
+                        contenttype_matches(content_type, 'application', 'yaml')
+                        or contenttype_matches(content_type, 'text', 'yaml')
+                        or contenttype_matches(content_type, 'text', 'x-yaml')
+                    )
                     and not isinstance(body, (str, bytes))
                 )
                 if is_json or is_structured_yaml:
@@ -234,7 +253,7 @@ class RESTClientObject:
                         headers=headers,
                         preload_content=False
                     )
-                elif content_type == 'application/x-www-form-urlencoded':
+                elif contenttype_matches(content_type, 'application', 'x-www-form-urlencoded'):
                     r = self.pool_manager.request(
                         method,
                         url,
@@ -244,7 +263,7 @@ class RESTClientObject:
                         headers=headers,
                         preload_content=False
                     )
-                elif content_type == 'multipart/form-data':
+                elif contenttype_matches(content_type, 'multipart', 'form-data'):
                     # must del headers['Content-Type'], or the correct
                     # Content-Type which generated by urllib3 will be
                     # overwritten.
@@ -272,7 +291,7 @@ class RESTClientObject:
                         headers=headers,
                         preload_content=False
                     )
-                elif headers['Content-Type'].startswith('text/') and isinstance(body, bool):
+                elif content_type.startswith('text/') and isinstance(body, bool):
                     request_body = "true" if body else "false"
                     r = self.pool_manager.request(
                         method,
diff --git a/samples/client/echo_api/python-disallowAdditionalPropertiesIfNotPresent/openapi_client/rest.py b/samples/client/echo_api/python-disallowAdditionalPropertiesIfNotPresent/openapi_client/rest.py
index 934eb3f8b794..ef3ed39f4679 100644
--- a/samples/client/echo_api/python-disallowAdditionalPropertiesIfNotPresent/openapi_client/rest.py
+++ b/samples/client/echo_api/python-disallowAdditionalPropertiesIfNotPresent/openapi_client/rest.py
@@ -37,6 +37,21 @@ def is_socks_proxy_url(url):
     else:
         return split_section[0].lower() in SUPPORTED_SOCKS_PROXIES
 
+def contenttype_matches(contenttype, maintype, subtype):
+    """Matches the given contenttype against the given type and subtype
+
+    :param contenttype: the content type to match
+    :param maintype: the expected maintype
+    :param subtype: the expected subtype
+    :return: `true` when the given content type matches the given type and subtype,
+        regardless of the presence of mime type parameters, otherwise returns `false`.
+    :rtype: bool
+    """
+    pattern = '{type}/(?:[^+;]+\\+)?{subtype}(?:[ \t]*;.*)?'.format(
+        type = re.escape(maintype),
+        subtype = re.escape(subtype),
+    )
+    return re.fullmatch(pattern, contenttype, re.IGNORECASE) is not None
 
 def should_bypass_proxies(url: str, no_proxy: str) -> bool:
     """Return whether ``url`` matches the comma-separated ``no_proxy`` rules."""
@@ -222,14 +237,18 @@ def request(
                 content_type = headers.get('Content-Type')
                 is_json = (
                     not content_type
-                    or re.search('json', content_type, re.IGNORECASE)
+                    or contenttype_matches(content_type, 'application', 'json')
                 )
                 # JSON is valid YAML 1.2, so structured YAML bodies can use
                 # the existing JSON serializer:
                 # https://yaml.org/spec/1.2.2/#13-relation-to-json
                 is_structured_yaml = (
                     content_type
-                    and re.search('yaml', content_type, re.IGNORECASE)
+                    and (
+                        contenttype_matches(content_type, 'application', 'yaml')
+                        or contenttype_matches(content_type, 'text', 'yaml')
+                        or contenttype_matches(content_type, 'text', 'x-yaml')
+                    )
                     and not isinstance(body, (str, bytes))
                 )
                 if is_json or is_structured_yaml:
@@ -244,7 +263,7 @@ def request(
                         headers=headers,
                         preload_content=False
                     )
-                elif content_type == 'application/x-www-form-urlencoded':
+                elif contenttype_matches(content_type, 'application', 'x-www-form-urlencoded'):
                     r = self.pool_manager.request(
                         method,
                         url,
@@ -254,7 +273,7 @@ def request(
                         headers=headers,
                         preload_content=False
                     )
-                elif content_type == 'multipart/form-data':
+                elif contenttype_matches(content_type, 'multipart', 'form-data'):
                     # must del headers['Content-Type'], or the correct
                     # Content-Type which generated by urllib3 will be
                     # overwritten.
@@ -282,7 +301,7 @@ def request(
                         headers=headers,
                         preload_content=False
                     )
-                elif headers['Content-Type'].startswith('text/') and isinstance(body, bool):
+                elif content_type.startswith('text/') and isinstance(body, bool):
                     request_body = "true" if body else "false"
                     r = self.pool_manager.request(
                         method,
diff --git a/samples/client/echo_api/python/openapi_client/rest.py b/samples/client/echo_api/python/openapi_client/rest.py
index b5a114226b79..5bd90b34957e 100644
--- a/samples/client/echo_api/python/openapi_client/rest.py
+++ b/samples/client/echo_api/python/openapi_client/rest.py
@@ -37,6 +37,21 @@ def is_socks_proxy_url(url):
     else:
         return split_section[0].lower() in SUPPORTED_SOCKS_PROXIES
 
+def contenttype_matches(contenttype, maintype, subtype):
+    """Matches the given contenttype against the given type and subtype
+
+    :param contenttype: the content type to match
+    :param maintype: the expected maintype
+    :param subtype: the expected subtype
+    :return: `true` when the given content type matches the given type and subtype,
+        regardless of the presence of mime type parameters, otherwise returns `false`.
+    :rtype: bool
+    """
+    pattern = '{type}/(?:[^+;]+\\+)?{subtype}(?:[ \t]*;.*)?'.format(
+        type = re.escape(maintype),
+        subtype = re.escape(subtype),
+    )
+    return re.fullmatch(pattern, contenttype, re.IGNORECASE) is not None
 
 def should_bypass_proxies(url: str, no_proxy: str) -> bool:
     """Return whether ``url`` matches the comma-separated ``no_proxy`` rules."""
@@ -222,14 +237,18 @@ def request(
                 content_type = headers.get('Content-Type')
                 is_json = (
                     not content_type
-                    or re.search('json', content_type, re.IGNORECASE)
+                    or contenttype_matches(content_type, 'application', 'json')
                 )
                 # JSON is valid YAML 1.2, so structured YAML bodies can use
                 # the existing JSON serializer:
                 # https://yaml.org/spec/1.2.2/#13-relation-to-json
                 is_structured_yaml = (
                     content_type
-                    and re.search('yaml', content_type, re.IGNORECASE)
+                    and (
+                        contenttype_matches(content_type, 'application', 'yaml')
+                        or contenttype_matches(content_type, 'text', 'yaml')
+                        or contenttype_matches(content_type, 'text', 'x-yaml')
+                    )
                     and not isinstance(body, (str, bytes))
                 )
                 if is_json or is_structured_yaml:
@@ -244,7 +263,7 @@ def request(
                         headers=headers,
                         preload_content=False
                     )
-                elif content_type == 'application/x-www-form-urlencoded':
+                elif contenttype_matches(content_type, 'application', 'x-www-form-urlencoded'):
                     r = self.pool_manager.request(
                         method,
                         url,
@@ -254,7 +273,7 @@ def request(
                         headers=headers,
                         preload_content=False
                     )
-                elif content_type == 'multipart/form-data':
+                elif contenttype_matches(content_type, 'multipart', 'form-data'):
                     # must del headers['Content-Type'], or the correct
                     # Content-Type which generated by urllib3 will be
                     # overwritten.
@@ -282,7 +301,7 @@ def request(
                         headers=headers,
                         preload_content=False
                     )
-                elif headers['Content-Type'].startswith('text/') and isinstance(body, bool):
+                elif content_type.startswith('text/') and isinstance(body, bool):
                     request_body = "true" if body else "false"
                     r = self.pool_manager.request(
                         method,
diff --git a/samples/openapi3/client/petstore/python-lazyImports/petstore_api/rest.py b/samples/openapi3/client/petstore/python-lazyImports/petstore_api/rest.py
index 5df0581723cc..075dca30faee 100644
--- a/samples/openapi3/client/petstore/python-lazyImports/petstore_api/rest.py
+++ b/samples/openapi3/client/petstore/python-lazyImports/petstore_api/rest.py
@@ -36,6 +36,21 @@ def is_socks_proxy_url(url):
     else:
         return split_section[0].lower() in SUPPORTED_SOCKS_PROXIES
 
+def contenttype_matches(contenttype, maintype, subtype):
+    """Matches the given contenttype against the given type and subtype
+
+    :param contenttype: the content type to match
+    :param maintype: the expected maintype
+    :param subtype: the expected subtype
+    :return: `true` when the given content type matches the given type and subtype,
+        regardless of the presence of mime type parameters, otherwise returns `false`.
+    :rtype: bool
+    """
+    pattern = '{type}/(?:[^+;]+\\+)?{subtype}(?:[ \t]*;.*)?'.format(
+        type = re.escape(maintype),
+        subtype = re.escape(subtype),
+    )
+    return re.fullmatch(pattern, contenttype, re.IGNORECASE) is not None
 
 def should_bypass_proxies(url: str, no_proxy: str) -> bool:
     """Return whether ``url`` matches the comma-separated ``no_proxy`` rules."""
@@ -221,14 +236,18 @@ def request(
                 content_type = headers.get('Content-Type')
                 is_json = (
                     not content_type
-                    or re.search('json', content_type, re.IGNORECASE)
+                    or contenttype_matches(content_type, 'application', 'json')
                 )
                 # JSON is valid YAML 1.2, so structured YAML bodies can use
                 # the existing JSON serializer:
                 # https://yaml.org/spec/1.2.2/#13-relation-to-json
                 is_structured_yaml = (
                     content_type
-                    and re.search('yaml', content_type, re.IGNORECASE)
+                    and (
+                        contenttype_matches(content_type, 'application', 'yaml')
+                        or contenttype_matches(content_type, 'text', 'yaml')
+                        or contenttype_matches(content_type, 'text', 'x-yaml')
+                    )
                     and not isinstance(body, (str, bytes))
                 )
                 if is_json or is_structured_yaml:
@@ -243,7 +262,7 @@ def request(
                         headers=headers,
                         preload_content=False
                     )
-                elif content_type == 'application/x-www-form-urlencoded':
+                elif contenttype_matches(content_type, 'application', 'x-www-form-urlencoded'):
                     r = self.pool_manager.request(
                         method,
                         url,
@@ -253,7 +272,7 @@ def request(
                         headers=headers,
                         preload_content=False
                     )
-                elif content_type == 'multipart/form-data':
+                elif contenttype_matches(content_type, 'multipart', 'form-data'):
                     # must del headers['Content-Type'], or the correct
                     # Content-Type which generated by urllib3 will be
                     # overwritten.
@@ -281,7 +300,7 @@ def request(
                         headers=headers,
                         preload_content=False
                     )
-                elif headers['Content-Type'].startswith('text/') and isinstance(body, bool):
+                elif content_type.startswith('text/') and isinstance(body, bool):
                     request_body = "true" if body else "false"
                     r = self.pool_manager.request(
                         method,
diff --git a/samples/openapi3/client/petstore/python/petstore_api/rest.py b/samples/openapi3/client/petstore/python/petstore_api/rest.py
index 5df0581723cc..075dca30faee 100755
--- a/samples/openapi3/client/petstore/python/petstore_api/rest.py
+++ b/samples/openapi3/client/petstore/python/petstore_api/rest.py
@@ -36,6 +36,21 @@ def is_socks_proxy_url(url):
     else:
         return split_section[0].lower() in SUPPORTED_SOCKS_PROXIES
 
+def contenttype_matches(contenttype, maintype, subtype):
+    """Matches the given contenttype against the given type and subtype
+
+    :param contenttype: the content type to match
+    :param maintype: the expected maintype
+    :param subtype: the expected subtype
+    :return: `true` when the given content type matches the given type and subtype,
+        regardless of the presence of mime type parameters, otherwise returns `false`.
+    :rtype: bool
+    """
+    pattern = '{type}/(?:[^+;]+\\+)?{subtype}(?:[ \t]*;.*)?'.format(
+        type = re.escape(maintype),
+        subtype = re.escape(subtype),
+    )
+    return re.fullmatch(pattern, contenttype, re.IGNORECASE) is not None
 
 def should_bypass_proxies(url: str, no_proxy: str) -> bool:
     """Return whether ``url`` matches the comma-separated ``no_proxy`` rules."""
@@ -221,14 +236,18 @@ def request(
                 content_type = headers.get('Content-Type')
                 is_json = (
                     not content_type
-                    or re.search('json', content_type, re.IGNORECASE)
+                    or contenttype_matches(content_type, 'application', 'json')
                 )
                 # JSON is valid YAML 1.2, so structured YAML bodies can use
                 # the existing JSON serializer:
                 # https://yaml.org/spec/1.2.2/#13-relation-to-json
                 is_structured_yaml = (
                     content_type
-                    and re.search('yaml', content_type, re.IGNORECASE)
+                    and (
+                        contenttype_matches(content_type, 'application', 'yaml')
+                        or contenttype_matches(content_type, 'text', 'yaml')
+                        or contenttype_matches(content_type, 'text', 'x-yaml')
+                    )
                     and not isinstance(body, (str, bytes))
                 )
                 if is_json or is_structured_yaml:
@@ -243,7 +262,7 @@ def request(
                         headers=headers,
                         preload_content=False
                     )
-                elif content_type == 'application/x-www-form-urlencoded':
+                elif contenttype_matches(content_type, 'application', 'x-www-form-urlencoded'):
                     r = self.pool_manager.request(
                         method,
                         url,
@@ -253,7 +272,7 @@ def request(
                         headers=headers,
                         preload_content=False
                     )
-                elif content_type == 'multipart/form-data':
+                elif contenttype_matches(content_type, 'multipart', 'form-data'):
                     # must del headers['Content-Type'], or the correct
                     # Content-Type which generated by urllib3 will be
                     # overwritten.
@@ -281,7 +300,7 @@ def request(
                         headers=headers,
                         preload_content=False
                     )
-                elif headers['Content-Type'].startswith('text/') and isinstance(body, bool):
+                elif content_type.startswith('text/') and isinstance(body, bool):
                     request_body = "true" if body else "false"
                     r = self.pool_manager.request(
                         method,