diff --git a/Doc/library/stdtypes.rst b/Doc/library/stdtypes.rst index 39aaa5da0786f8..37c78aff8d3779 100644 --- a/Doc/library/stdtypes.rst +++ b/Doc/library/stdtypes.rst @@ -5346,6 +5346,15 @@ creation:: >>> type(l) + +Additionally, instances of ``GenericAlias`` are not classes at runtime, even though they behave like classes (e.g. they can be instantiated):: + + >>> import inspect + >>> inspect.isclass(list[int]) + False + +This is true for :ref:`user-defined generics ` also. + Calling :func:`repr` or :func:`str` on a generic shows the parameterized type:: >>> repr(list[int]) diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py index 8c55ba4623e719..14fe9921c44388 100644 --- a/Lib/test/test_typing.py +++ b/Lib/test/test_typing.py @@ -5638,6 +5638,27 @@ def foo(x: T): foo(42) + def test_genericalias_instance_isclass(self): + # test against user-defined generic classes + T = TypeVar('T') + + class Node(Generic[T]): + def __init__(self, label: T, + left: 'Node[T] | None' = None, + right: 'Node[T] | None' = None): + self.label = label + self.left = left + self.right = right + + self.assertTrue(inspect.isclass(Node)) + self.assertFalse(inspect.isclass(Node[int])) + self.assertFalse(inspect.isclass(Node[str])) + + # test against standard generic classes + self.assertFalse(inspect.isclass(set[int])) + self.assertFalse(inspect.isclass(list[bytes])) + self.assertFalse(inspect.isclass(dict[str, str])) + def test_implicit_any(self): T = TypeVar('T') diff --git a/Lib/typing.py b/Lib/typing.py index 2baf655256d1eb..12071f0d3a30af 100644 --- a/Lib/typing.py +++ b/Lib/typing.py @@ -1283,31 +1283,34 @@ def __dir__(self): 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] - + """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] + + Note that objects of this class is not considered to be a class (e.g by `inspect.isclass`), + even though they behave like them. + """ def __init__(self, origin, args, *, inst=True, name=None): super().__init__(origin, inst=inst, name=name) if not isinstance(args, tuple): @@ -1339,20 +1342,21 @@ def __ror__(self, left): @_tp_cache def __getitem__(self, args): - # Parameterizes an already-parameterized object. - # - # For example, we arrive here doing something like: - # T1 = TypeVar('T1') - # T2 = TypeVar('T2') - # T3 = TypeVar('T3') - # class A(Generic[T1]): pass - # B = A[T2] # B is a _GenericAlias - # C = B[T3] # Invokes _GenericAlias.__getitem__ - # - # We also arrive here when parameterizing a generic `Callable` alias: - # T = TypeVar('T') - # C = Callable[[T], None] - # C[int] # Invokes _GenericAlias.__getitem__ + """Parameterizes an already-parameterized object. + + For example, we arrive here doing something like: + T1 = TypeVar('T1') + T2 = TypeVar('T2') + T3 = TypeVar('T3') + class A(Generic[T1]): pass + B = A[T2] # B is a _GenericAlias + C = B[T3] # Invokes _GenericAlias.__getitem__ + + We also arrive here when parameterizing a generic `Callable` alias: + T = TypeVar('T') + C = Callable[[T], None] + C[int] # Invokes _GenericAlias.__getitem__ + """ if self.__origin__ in (Generic, Protocol): # Can't subscript Generic[...] or Protocol[...]. @@ -1369,20 +1373,20 @@ def __getitem__(self, args): return r def _determine_new_args(self, args): - # Determines new __args__ for __getitem__. - # - # For example, suppose we had: - # T1 = TypeVar('T1') - # T2 = TypeVar('T2') - # class A(Generic[T1, T2]): pass - # T3 = TypeVar('T3') - # B = A[int, T3] - # C = B[str] - # `B.__args__` is `(int, T3)`, so `C.__args__` should be `(int, str)`. - # Unfortunately, this is harder than it looks, because if `T3` is - # anything more exotic than a plain `TypeVar`, we need to consider - # edge cases. - + """Determines new __args__ for __getitem__. + + For example, suppose we had: + T1 = TypeVar('T1') + T2 = TypeVar('T2') + class A(Generic[T1, T2]): pass + T3 = TypeVar('T3') + B = A[int, T3] + C = B[str] + `B.__args__` is `(int, T3)`, so `C.__args__` should be `(int, str)`. + Unfortunately, this is harder than it looks, because if `T3` is + anything more exotic than a plain `TypeVar`, we need to consider + edge cases. + """ params = self.__parameters__ # In the example above, this would be {T3: str} for param in params: