Function in_

src/attr/validators.py:259–291

A validator that raises a `ValueError` if the initializer is called with a value that does not belong in the *options* provided. The check is performed using ``value in options``, so *options* has to support that operation. To keep the validator hashable, dicts, lists, and set

(options)

def in_(options):
    class="st">"""
    A validator that raises a `ValueError` if the initializer is called with a
    value that does not belong in the *options* provided.

    The check is performed using ``value in options``, so *options* has to
    support that operation.

    To keep the validator hashable, dicts, lists, and sets are transparently
    transformed into a `tuple`.

    Args:
        options: Allowed options.

    Raises:
        ValueError:
            With a human readable error message, the attribute (of type
            `attrs.Attribute`), the expected options, and the value it got.

    .. versionadded:: 17.1.0
    .. versionchanged:: 22.1.0
       The ValueError was incomplete until now and only contained the human
       readable error message. Now it contains all the information that has
       been promised since 17.1.0.
    .. versionchanged:: 24.1.0
       *options* that are a list, dict, or a set are now transformed into a
       tuple to keep the validator hashable.
    class="st">"""
    repr_options = options
    if isinstance(options, (list, dict, set)):
        options = tuple(options)

    return _InValidator(options, repr_options)


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