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Pydantic · Decorator

field_validator

field_validator lets you check or change model fields during validation. It supports four modes: after, before, plain, and wrap.

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Syntax

field_validator(*fields: str, mode: Literal['before', 'after', 'plain', 'wrap'] = 'after', check_fields: bool | None = None, json_schema_input_type: Any = PydanticUndefined)

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  • AfterValidator
  • BeforeValidator
  • PlainValidator
  • WrapValidator
  • model_validator
  • ValidationInfo

Source: Validators | Pydantic Docs. Checked 2026-11-03.