Function optional

src/attr/validators.py:214–232

A validator that makes an attribute optional. An optional attribute is one which can be set to `None` in addition to satisfying the requirements of the sub-validator. Args: validator (typing.Callable | tuple[typing.Callable] | list[typing.Callable]):

(validator)

def optional(validator):
    """
    A validator that makes an attribute optional.  An optional attribute is one
    which can be set to `None` in addition to satisfying the requirements of
    the sub-validator.

    Args:
        validator
            (typing.Callable | tuple[typing.Callable] | list[typing.Callable]):
            A validator (or validators) that is used for non-`None` values.

    .. versionadded:: 15.1.0
    .. versionchanged:: 17.1.0 *validator* can be a list of validators.
    .. versionchanged:: 23.1.0 *validator* can also be a tuple of validators.
    """
    if isinstance(validator, (list, tuple)):
        return _OptionalValidator(_AndValidator(validator))

    return _OptionalValidator(validator)


@attrs(repr=False, slots=True, unsafe_hash=True)