Class _GenericAlias

Lib/typing.py:1315–1533

class _GenericAlias(_BaseGenericAlias, _root=True):
    # The type of parameterized generics.
    #
    # That is, for example, `type(List[int])` is `_GenericAlias`.
    #
    # Objects which are instances of this class include:
    # * Parameterized container types, e.g. `Tuple[int]`, `List[int]`.
    #  * Note that native container types, e.g. `tuple`, `list`, use
    #    `types.GenericAlias` instead.
    # * Parameterized classes:
    #     class C[T]: pass
    #     # C[int] is a _GenericAlias
    # * `Callable` aliases, generic `Callable` aliases, and
    #   parameterized `Callable` aliases:
    #     T = TypeVar('T')
    #     # _CallableGenericAlias inherits from _GenericAlias.
    #     A = Callable[[], None]  # _CallableGenericAlias
    #     B = Callable[[T], None]  # _CallableGenericAlias
    #     C = B[int]  # _CallableGenericAlias
    # * Parameterized `Final`, `ClassVar`, `TypeGuard`, and `TypeIs`:
    #     # All _GenericAlias
    #     Final[int]
    #     ClassVar[float]
    #     TypeGuard[bool]
    #     TypeIs[range]

    def __init__(self, origin, args, *, inst=True, name=None):
        super().__init__(origin, inst=inst, name=name)
        if not isinstance(args, tuple):
            args = (args,)
        self.__args__ = tuple(... if a is _TypingEllipsis else
                              a for a in args)
        enforce_default_ordering = origin in (Generic, Protocol)
        self.__parameters__ = _collect_type_parameters(
            args,
            enforce_default_ordering=enforce_default_ordering,
        )
        if not name:
            self.__module__ = origin.__module__

    def __eq__(self, other):
        if not isinstance(other, _GenericAlias):
            return NotImplemented
        return (self.__origin__ == other.__origin__
                and self.__args__ == other.__args__)

    def __hash__(self):
        return hash((self.__origin__, self.__args__))

    def __or__(self, right):
        return Union[self, right]

    def __ror__(self, left):
        return Union[left, self]

    @_tp_cache
    def __getitem__(self, args):
        # Parameterizes an already-parameterized object.