Function TypeForm

Lib/typing.py:907–928

A special form representing the value that results from the evaluation of a type expression. This value encodes the information supplied in the type expression, and it represents the type described by that type expression. When used in a type expression, TypeForm describes a set of

(self, parameters)

@_TypeFormForm
def TypeForm(self, parameters):
    """A special form representing the value that results from the evaluation
    of a type expression.

    This value encodes the information supplied in the type expression, and it
    represents the type described by that type expression.

    When used in a type expression, TypeForm describes a set of type form
    objects. It accepts a single type argument, which must be a valid type
    expression. ``TypeForm[T]`` describes the set of all type form objects that
    represent the type T or types that are assignable to T.

    Usage::

        def cast[T](typ: TypeForm[T], value: Any) -> T: ...

        reveal_type(cast(int, "x"))  # int

    See PEP 747 for more information.
    """
    item = _type_check(parameters, f'{self} accepts only single type.')
    return _GenericAlias(self, (item,))


@_SpecialForm