Validate Call

Decorator for validating function calls.

validate_call

validate_call(
    *,
    config: ConfigDict | None = None,
    validate_return: bool = False
) -> Callable[[AnyCallableT], AnyCallableT]

validate_call(func: AnyCallableT) -> AnyCallableT

validate_call(
    func: AnyCallableT | None = None,
    /,
    *,
    config: ConfigDict | None = None,
    validate_return: bool = False,
) -> AnyCallableT | Callable[[AnyCallableT], AnyCallableT]

Usage Documentation

Validation Decorator

Returns a wrapper around the function that validates the arguments and, optionally, the return value.

Usage may be either as a plain decorator @validate_call or with arguments (@validate_call(...)).

When a decorated call fails, the ValidationError reports the rejected argument and value. Logfire can retain the complete call input and surrounding trace context — see Troubleshooting validation errors.

Parameters:

Name	Type	Description	Default
func	AnyCallableT | None	The function to be wrapped.	None
config	ConfigDict | None	The configuration dictionary.	None
validate_return	bool	Whether to validate the return value.	False

Returns:

Type	Description
AnyCallableT | Callable[[AnyCallableT], AnyCallableT]	The decorated function.

Source code in pydantic/validate_call_decorator.py

def validate_call(
    func: AnyCallableT | None = None,
    /,
    *,
    config: ConfigDict | None = None,
    validate_return: bool = False,
) -> AnyCallableT | Callable[[AnyCallableT], AnyCallableT]:
    """!!! abstract "Usage Documentation"
        [Validation Decorator](../concepts/validation_decorator.md)

    Returns a wrapper around the function that validates the arguments and, optionally, the return value.

    Usage may be either as a plain decorator `@validate_call` or with arguments (`@validate_call(...)`).

    When a decorated call fails, the [`ValidationError`][pydantic_core.ValidationError] reports the
    rejected argument and value. [Logfire](../integrations/logfire.md) can retain the complete call input
    and surrounding trace context — see [Troubleshooting validation errors](../errors/troubleshooting.md).

    Args:
        func: The function to be wrapped.
        config: The configuration dictionary.
        validate_return: Whether to validate the return value.

    Returns:
        The decorated function.
    """
    parent_namespace = _typing_extra.parent_frame_namespace()

    def validate(function: AnyCallableT) -> AnyCallableT:
        _check_function_type(function)
        validate_call_wrapper = _validate_call.ValidateCallWrapper(
            cast(_generate_schema.ValidateCallSupportedTypes, function), config, validate_return, parent_namespace
        )
        return _validate_call.update_wrapper_attributes(function, validate_call_wrapper.__call__)  # type: ignore

    if func is not None:
        return validate(func)
    else:
        return validate