field_validator

Decorate methods on the class indicating that they should be used to validate fields.

def field_validator(
    field: str,
    *fields: str,
    mode: FieldValidatorModes = 'after',
    check_fields: bool | None = None,
    json_schema_input_type: Any = PydanticUndefined
) - > Callable[[Any], Any]

Decorate methods on the class indicating that they should be used to validate fields.

Parameters

Name	Type	Description
field	str	The first field name the validator should apply to; must be a string.
*fields	str	Additional field names the validator should apply to.
mode	FieldValidatorModes = 'after'	Specifies whether to validate the fields before or after standard validation, or to use 'plain' or 'wrap' logic.
check_fields	`bool	None` = None
json_schema_input_type	Any = PydanticUndefined	The input type used to generate the appropriate JSON Schema; only valid when mode is 'before', 'plain', or 'wrap'.

Returns

Type	Description
Callable[[Any], Any]	A decorator function that wraps the target method and registers it as a Pydantic field validator.