diff --git a/modules/openapi-generator/src/main/resources/python/model_generic.mustache b/modules/openapi-generator/src/main/resources/python/model_generic.mustache
index 1b9d0f7d3fd8..ff65695b605a 100644
--- a/modules/openapi-generator/src/main/resources/python/model_generic.mustache
+++ b/modules/openapi-generator/src/main/resources/python/model_generic.mustache
@@ -38,7 +38,7 @@ class {{classname}}({{#parent}}{{{.}}}{{/parent}}{{^parent}}BaseModel{{/parent}}
 {{#vars}}
     {{#vendorExtensions.x-regex}}
 
-    @field_validator('{{{name}}}')
+    @field_validator('{{{name}}}', mode="before")
     def {{{name}}}_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         {{^required}}
@@ -53,10 +53,7 @@ class {{classname}}({{#parent}}{{{.}}}{{/parent}}{{^parent}}BaseModel{{/parent}}
 
         {{/isNullable}}
         {{/required}}
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"{{{.}}}", value{{#vendorExtensions.x-modifiers}} ,re.{{{.}}}{{/vendorExtensions.x-modifiers}}):
+        if isinstance(value, str) and not re.match(r"{{{.}}}", value{{#vendorExtensions.x-modifiers}} ,re.{{{.}}}{{/vendorExtensions.x-modifiers}}):
             raise ValueError(r"must validate the regular expression {{{vendorExtensions.x-pattern}}}")
         return value
     {{/vendorExtensions.x-regex}}
diff --git a/samples/openapi3/client/petstore/python-aiohttp/petstore_api/models/format_test.py b/samples/openapi3/client/petstore/python-aiohttp/petstore_api/models/format_test.py
index 9fdebaa549d2..92f3cacf7f91 100644
--- a/samples/openapi3/client/petstore/python-aiohttp/petstore_api/models/format_test.py
+++ b/samples/openapi3/client/petstore/python-aiohttp/petstore_api/models/format_test.py
@@ -50,55 +50,43 @@ class FormatTest(BaseModel):
     pattern_with_digits_and_delimiter: Optional[Annotated[str, Field(strict=True)]] = Field(default=None, description="A string starting with 'image_' (case insensitive) and one to three digits following i.e. Image_01.")
     __properties: ClassVar[List[str]] = ["integer", "int32", "int64", "number", "float", "double", "decimal", "string", "string_with_double_quote_pattern", "byte", "binary", "date", "dateTime", "uuid", "password", "pattern_with_digits", "pattern_with_digits_and_delimiter"]
 
-    @field_validator('string')
+    @field_validator('string', mode="before")
     def string_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"[a-z]", value ,re.IGNORECASE):
+        if isinstance(value, str) and not re.match(r"[a-z]", value ,re.IGNORECASE):
             raise ValueError(r"must validate the regular expression /[a-z]/i")
         return value
 
-    @field_validator('string_with_double_quote_pattern')
+    @field_validator('string_with_double_quote_pattern', mode="before")
     def string_with_double_quote_pattern_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"this is \"something\"", value):
+        if isinstance(value, str) and not re.match(r"this is \"something\"", value):
             raise ValueError(r"must validate the regular expression /this is \"something\"/")
         return value
 
-    @field_validator('pattern_with_digits')
+    @field_validator('pattern_with_digits', mode="before")
     def pattern_with_digits_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"^\d{10}$", value):
+        if isinstance(value, str) and not re.match(r"^\d{10}$", value):
             raise ValueError(r"must validate the regular expression /^\d{10}$/")
         return value
 
-    @field_validator('pattern_with_digits_and_delimiter')
+    @field_validator('pattern_with_digits_and_delimiter', mode="before")
     def pattern_with_digits_and_delimiter_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"^image_\d{1,3}$", value ,re.IGNORECASE):
+        if isinstance(value, str) and not re.match(r"^image_\d{1,3}$", value ,re.IGNORECASE):
             raise ValueError(r"must validate the regular expression /^image_\d{1,3}$/i")
         return value
 
diff --git a/samples/openapi3/client/petstore/python-aiohttp/petstore_api/models/nullable_property.py b/samples/openapi3/client/petstore/python-aiohttp/petstore_api/models/nullable_property.py
index f396a5f10045..819cc52809b9 100644
--- a/samples/openapi3/client/petstore/python-aiohttp/petstore_api/models/nullable_property.py
+++ b/samples/openapi3/client/petstore/python-aiohttp/petstore_api/models/nullable_property.py
@@ -32,16 +32,13 @@ class NullableProperty(BaseModel):
     name: Optional[Annotated[str, Field(strict=True)]]
     __properties: ClassVar[List[str]] = ["id", "name"]
 
-    @field_validator('name')
+    @field_validator('name', mode="before")
     def name_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"^[A-Z].*", value):
+        if isinstance(value, str) and not re.match(r"^[A-Z].*", value):
             raise ValueError(r"must validate the regular expression /^[A-Z].*/")
         return value
 
diff --git a/samples/openapi3/client/petstore/python-aiohttp/petstore_api/models/uuid_with_pattern.py b/samples/openapi3/client/petstore/python-aiohttp/petstore_api/models/uuid_with_pattern.py
index 9936e04769f1..31c7b3567a6c 100644
--- a/samples/openapi3/client/petstore/python-aiohttp/petstore_api/models/uuid_with_pattern.py
+++ b/samples/openapi3/client/petstore/python-aiohttp/petstore_api/models/uuid_with_pattern.py
@@ -31,16 +31,13 @@ class UuidWithPattern(BaseModel):
     id: Optional[UUID] = None
     __properties: ClassVar[List[str]] = ["id"]
 
-    @field_validator('id')
+    @field_validator('id', mode="before")
     def id_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$", value):
+        if isinstance(value, str) and not re.match(r"^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$", value):
             raise ValueError(r"must validate the regular expression /^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$/")
         return value
 
diff --git a/samples/openapi3/client/petstore/python-httpx/petstore_api/models/format_test.py b/samples/openapi3/client/petstore/python-httpx/petstore_api/models/format_test.py
index 9fdebaa549d2..92f3cacf7f91 100644
--- a/samples/openapi3/client/petstore/python-httpx/petstore_api/models/format_test.py
+++ b/samples/openapi3/client/petstore/python-httpx/petstore_api/models/format_test.py
@@ -50,55 +50,43 @@ class FormatTest(BaseModel):
     pattern_with_digits_and_delimiter: Optional[Annotated[str, Field(strict=True)]] = Field(default=None, description="A string starting with 'image_' (case insensitive) and one to three digits following i.e. Image_01.")
     __properties: ClassVar[List[str]] = ["integer", "int32", "int64", "number", "float", "double", "decimal", "string", "string_with_double_quote_pattern", "byte", "binary", "date", "dateTime", "uuid", "password", "pattern_with_digits", "pattern_with_digits_and_delimiter"]
 
-    @field_validator('string')
+    @field_validator('string', mode="before")
     def string_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"[a-z]", value ,re.IGNORECASE):
+        if isinstance(value, str) and not re.match(r"[a-z]", value ,re.IGNORECASE):
             raise ValueError(r"must validate the regular expression /[a-z]/i")
         return value
 
-    @field_validator('string_with_double_quote_pattern')
+    @field_validator('string_with_double_quote_pattern', mode="before")
     def string_with_double_quote_pattern_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"this is \"something\"", value):
+        if isinstance(value, str) and not re.match(r"this is \"something\"", value):
             raise ValueError(r"must validate the regular expression /this is \"something\"/")
         return value
 
-    @field_validator('pattern_with_digits')
+    @field_validator('pattern_with_digits', mode="before")
     def pattern_with_digits_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"^\d{10}$", value):
+        if isinstance(value, str) and not re.match(r"^\d{10}$", value):
             raise ValueError(r"must validate the regular expression /^\d{10}$/")
         return value
 
-    @field_validator('pattern_with_digits_and_delimiter')
+    @field_validator('pattern_with_digits_and_delimiter', mode="before")
     def pattern_with_digits_and_delimiter_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"^image_\d{1,3}$", value ,re.IGNORECASE):
+        if isinstance(value, str) and not re.match(r"^image_\d{1,3}$", value ,re.IGNORECASE):
             raise ValueError(r"must validate the regular expression /^image_\d{1,3}$/i")
         return value
 
diff --git a/samples/openapi3/client/petstore/python-httpx/petstore_api/models/nullable_property.py b/samples/openapi3/client/petstore/python-httpx/petstore_api/models/nullable_property.py
index f396a5f10045..819cc52809b9 100644
--- a/samples/openapi3/client/petstore/python-httpx/petstore_api/models/nullable_property.py
+++ b/samples/openapi3/client/petstore/python-httpx/petstore_api/models/nullable_property.py
@@ -32,16 +32,13 @@ class NullableProperty(BaseModel):
     name: Optional[Annotated[str, Field(strict=True)]]
     __properties: ClassVar[List[str]] = ["id", "name"]
 
-    @field_validator('name')
+    @field_validator('name', mode="before")
     def name_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"^[A-Z].*", value):
+        if isinstance(value, str) and not re.match(r"^[A-Z].*", value):
             raise ValueError(r"must validate the regular expression /^[A-Z].*/")
         return value
 
diff --git a/samples/openapi3/client/petstore/python-httpx/petstore_api/models/uuid_with_pattern.py b/samples/openapi3/client/petstore/python-httpx/petstore_api/models/uuid_with_pattern.py
index 9936e04769f1..31c7b3567a6c 100644
--- a/samples/openapi3/client/petstore/python-httpx/petstore_api/models/uuid_with_pattern.py
+++ b/samples/openapi3/client/petstore/python-httpx/petstore_api/models/uuid_with_pattern.py
@@ -31,16 +31,13 @@ class UuidWithPattern(BaseModel):
     id: Optional[UUID] = None
     __properties: ClassVar[List[str]] = ["id"]
 
-    @field_validator('id')
+    @field_validator('id', mode="before")
     def id_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$", value):
+        if isinstance(value, str) and not re.match(r"^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$", value):
             raise ValueError(r"must validate the regular expression /^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$/")
         return value
 
diff --git a/samples/openapi3/client/petstore/python-lazyImports/petstore_api/models/format_test.py b/samples/openapi3/client/petstore/python-lazyImports/petstore_api/models/format_test.py
index a26767d39f56..1c0459f06e04 100644
--- a/samples/openapi3/client/petstore/python-lazyImports/petstore_api/models/format_test.py
+++ b/samples/openapi3/client/petstore/python-lazyImports/petstore_api/models/format_test.py
@@ -51,55 +51,43 @@ class FormatTest(BaseModel):
     additional_properties: Dict[str, Any] = {}
     __properties: ClassVar[List[str]] = ["integer", "int32", "int64", "number", "float", "double", "decimal", "string", "string_with_double_quote_pattern", "byte", "binary", "date", "dateTime", "uuid", "password", "pattern_with_digits", "pattern_with_digits_and_delimiter"]
 
-    @field_validator('string')
+    @field_validator('string', mode="before")
     def string_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"[a-z]", value ,re.IGNORECASE):
+        if isinstance(value, str) and not re.match(r"[a-z]", value ,re.IGNORECASE):
             raise ValueError(r"must validate the regular expression /[a-z]/i")
         return value
 
-    @field_validator('string_with_double_quote_pattern')
+    @field_validator('string_with_double_quote_pattern', mode="before")
     def string_with_double_quote_pattern_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"this is \"something\"", value):
+        if isinstance(value, str) and not re.match(r"this is \"something\"", value):
             raise ValueError(r"must validate the regular expression /this is \"something\"/")
         return value
 
-    @field_validator('pattern_with_digits')
+    @field_validator('pattern_with_digits', mode="before")
     def pattern_with_digits_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"^\d{10}$", value):
+        if isinstance(value, str) and not re.match(r"^\d{10}$", value):
             raise ValueError(r"must validate the regular expression /^\d{10}$/")
         return value
 
-    @field_validator('pattern_with_digits_and_delimiter')
+    @field_validator('pattern_with_digits_and_delimiter', mode="before")
     def pattern_with_digits_and_delimiter_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"^image_\d{1,3}$", value ,re.IGNORECASE):
+        if isinstance(value, str) and not re.match(r"^image_\d{1,3}$", value ,re.IGNORECASE):
             raise ValueError(r"must validate the regular expression /^image_\d{1,3}$/i")
         return value
 
diff --git a/samples/openapi3/client/petstore/python-lazyImports/petstore_api/models/nullable_property.py b/samples/openapi3/client/petstore/python-lazyImports/petstore_api/models/nullable_property.py
index 0d838a27738e..38c9b57b0652 100644
--- a/samples/openapi3/client/petstore/python-lazyImports/petstore_api/models/nullable_property.py
+++ b/samples/openapi3/client/petstore/python-lazyImports/petstore_api/models/nullable_property.py
@@ -33,16 +33,13 @@ class NullableProperty(BaseModel):
     additional_properties: Dict[str, Any] = {}
     __properties: ClassVar[List[str]] = ["id", "name"]
 
-    @field_validator('name')
+    @field_validator('name', mode="before")
     def name_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"^[A-Z].*", value):
+        if isinstance(value, str) and not re.match(r"^[A-Z].*", value):
             raise ValueError(r"must validate the regular expression /^[A-Z].*/")
         return value
 
diff --git a/samples/openapi3/client/petstore/python-lazyImports/petstore_api/models/uuid_with_pattern.py b/samples/openapi3/client/petstore/python-lazyImports/petstore_api/models/uuid_with_pattern.py
index e86c87f16359..5dd5ec4932ed 100644
--- a/samples/openapi3/client/petstore/python-lazyImports/petstore_api/models/uuid_with_pattern.py
+++ b/samples/openapi3/client/petstore/python-lazyImports/petstore_api/models/uuid_with_pattern.py
@@ -32,16 +32,13 @@ class UuidWithPattern(BaseModel):
     additional_properties: Dict[str, Any] = {}
     __properties: ClassVar[List[str]] = ["id"]
 
-    @field_validator('id')
+    @field_validator('id', mode="before")
     def id_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$", value):
+        if isinstance(value, str) and not re.match(r"^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$", value):
             raise ValueError(r"must validate the regular expression /^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$/")
         return value
 
diff --git a/samples/openapi3/client/petstore/python/petstore_api/models/format_test.py b/samples/openapi3/client/petstore/python/petstore_api/models/format_test.py
index a26767d39f56..1c0459f06e04 100644
--- a/samples/openapi3/client/petstore/python/petstore_api/models/format_test.py
+++ b/samples/openapi3/client/petstore/python/petstore_api/models/format_test.py
@@ -51,55 +51,43 @@ class FormatTest(BaseModel):
     additional_properties: Dict[str, Any] = {}
     __properties: ClassVar[List[str]] = ["integer", "int32", "int64", "number", "float", "double", "decimal", "string", "string_with_double_quote_pattern", "byte", "binary", "date", "dateTime", "uuid", "password", "pattern_with_digits", "pattern_with_digits_and_delimiter"]
 
-    @field_validator('string')
+    @field_validator('string', mode="before")
     def string_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"[a-z]", value ,re.IGNORECASE):
+        if isinstance(value, str) and not re.match(r"[a-z]", value ,re.IGNORECASE):
             raise ValueError(r"must validate the regular expression /[a-z]/i")
         return value
 
-    @field_validator('string_with_double_quote_pattern')
+    @field_validator('string_with_double_quote_pattern', mode="before")
     def string_with_double_quote_pattern_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"this is \"something\"", value):
+        if isinstance(value, str) and not re.match(r"this is \"something\"", value):
             raise ValueError(r"must validate the regular expression /this is \"something\"/")
         return value
 
-    @field_validator('pattern_with_digits')
+    @field_validator('pattern_with_digits', mode="before")
     def pattern_with_digits_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"^\d{10}$", value):
+        if isinstance(value, str) and not re.match(r"^\d{10}$", value):
             raise ValueError(r"must validate the regular expression /^\d{10}$/")
         return value
 
-    @field_validator('pattern_with_digits_and_delimiter')
+    @field_validator('pattern_with_digits_and_delimiter', mode="before")
     def pattern_with_digits_and_delimiter_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"^image_\d{1,3}$", value ,re.IGNORECASE):
+        if isinstance(value, str) and not re.match(r"^image_\d{1,3}$", value ,re.IGNORECASE):
             raise ValueError(r"must validate the regular expression /^image_\d{1,3}$/i")
         return value
 
diff --git a/samples/openapi3/client/petstore/python/petstore_api/models/nullable_property.py b/samples/openapi3/client/petstore/python/petstore_api/models/nullable_property.py
index 0d838a27738e..38c9b57b0652 100644
--- a/samples/openapi3/client/petstore/python/petstore_api/models/nullable_property.py
+++ b/samples/openapi3/client/petstore/python/petstore_api/models/nullable_property.py
@@ -33,16 +33,13 @@ class NullableProperty(BaseModel):
     additional_properties: Dict[str, Any] = {}
     __properties: ClassVar[List[str]] = ["id", "name"]
 
-    @field_validator('name')
+    @field_validator('name', mode="before")
     def name_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"^[A-Z].*", value):
+        if isinstance(value, str) and not re.match(r"^[A-Z].*", value):
             raise ValueError(r"must validate the regular expression /^[A-Z].*/")
         return value
 
diff --git a/samples/openapi3/client/petstore/python/petstore_api/models/uuid_with_pattern.py b/samples/openapi3/client/petstore/python/petstore_api/models/uuid_with_pattern.py
index e86c87f16359..5dd5ec4932ed 100644
--- a/samples/openapi3/client/petstore/python/petstore_api/models/uuid_with_pattern.py
+++ b/samples/openapi3/client/petstore/python/petstore_api/models/uuid_with_pattern.py
@@ -32,16 +32,13 @@ class UuidWithPattern(BaseModel):
     additional_properties: Dict[str, Any] = {}
     __properties: ClassVar[List[str]] = ["id"]
 
-    @field_validator('id')
+    @field_validator('id', mode="before")
     def id_validate_regular_expression(cls, value):
         """Validates the regular expression"""
         if value is None:
             return value
 
-        if not isinstance(value, str):
-            value = str(value)
-
-        if not re.match(r"^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$", value):
+        if isinstance(value, str) and not re.match(r"^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$", value):
             raise ValueError(r"must validate the regular expression /^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$/")
         return value