diff options
| -rw-r--r-- | Doc/library/typing.rst | 26 | ||||
| -rw-r--r-- | Lib/test/test_typing.py | 11 | ||||
| -rw-r--r-- | Lib/typing.py | 21 | ||||
| -rw-r--r-- | Misc/NEWS.d/next/Library/2024-05-06-08-23-01.gh-issue-118648.OVA3jJ.rst | 2 |
4 files changed, 51 insertions, 9 deletions
diff --git a/Doc/library/typing.rst b/Doc/library/typing.rst index e062872..652a3f1 100644 --- a/Doc/library/typing.rst +++ b/Doc/library/typing.rst @@ -3648,8 +3648,14 @@ Aliases to asynchronous ABCs in :mod:`collections.abc` is no ``ReturnType`` type parameter. As with :class:`Generator`, the ``SendType`` behaves contravariantly. - If your generator will only yield values, set the ``SendType`` to - ``None``:: + The ``SendType`` defaults to :const:`!None`:: + + async def infinite_stream(start: int) -> AsyncGenerator[int]: + while True: + yield start + start = await increment(start) + + It is also possible to set this type explicitly:: async def infinite_stream(start: int) -> AsyncGenerator[int, None]: while True: @@ -3671,6 +3677,9 @@ Aliases to asynchronous ABCs in :mod:`collections.abc` now supports subscripting (``[]``). See :pep:`585` and :ref:`types-genericalias`. + .. versionchanged:: 3.13 + The ``SendType`` parameter now has a default. + .. class:: AsyncIterable(Generic[T_co]) Deprecated alias to :class:`collections.abc.AsyncIterable`. @@ -3754,8 +3763,14 @@ Aliases to other ABCs in :mod:`collections.abc` of :class:`Generator` behaves contravariantly, not covariantly or invariantly. - If your generator will only yield values, set the ``SendType`` and - ``ReturnType`` to ``None``:: + The ``SendType`` and ``ReturnType`` parameters default to :const:`!None`:: + + def infinite_stream(start: int) -> Generator[int]: + while True: + yield start + start += 1 + + It is also possible to set these types explicitly:: def infinite_stream(start: int) -> Generator[int, None, None]: while True: @@ -3774,6 +3789,9 @@ Aliases to other ABCs in :mod:`collections.abc` :class:`collections.abc.Generator` now supports subscripting (``[]``). See :pep:`585` and :ref:`types-genericalias`. + .. versionchanged:: 3.13 + Default values for the send and return types were added. + .. class:: Hashable Deprecated alias to :class:`collections.abc.Hashable`. diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py index 112db03..8f0be1f 100644 --- a/Lib/test/test_typing.py +++ b/Lib/test/test_typing.py @@ -7289,6 +7289,17 @@ class CollectionsAbcTests(BaseTestCase): g = foo() self.assertIsSubclass(type(g), typing.Generator) + def test_generator_default(self): + g1 = typing.Generator[int] + g2 = typing.Generator[int, None, None] + self.assertEqual(get_args(g1), (int, type(None), type(None))) + self.assertEqual(get_args(g1), get_args(g2)) + + g3 = typing.Generator[int, float] + g4 = typing.Generator[int, float, None] + self.assertEqual(get_args(g3), (int, float, type(None))) + self.assertEqual(get_args(g3), get_args(g4)) + def test_no_generator_instantiation(self): with self.assertRaises(TypeError): typing.Generator() diff --git a/Lib/typing.py b/Lib/typing.py index ff0e9b8..c159fcf 100644 --- a/Lib/typing.py +++ b/Lib/typing.py @@ -1328,7 +1328,7 @@ class _BaseGenericAlias(_Final, _root=True): raise AttributeError(attr) def __setattr__(self, attr, val): - if _is_dunder(attr) or attr in {'_name', '_inst', '_nparams'}: + if _is_dunder(attr) or attr in {'_name', '_inst', '_nparams', '_defaults'}: super().__setattr__(attr, val) else: setattr(self.__origin__, attr, val) @@ -1578,11 +1578,12 @@ class _GenericAlias(_BaseGenericAlias, _root=True): # parameters are accepted (needs custom __getitem__). class _SpecialGenericAlias(_NotIterable, _BaseGenericAlias, _root=True): - def __init__(self, origin, nparams, *, inst=True, name=None): + def __init__(self, origin, nparams, *, inst=True, name=None, defaults=()): if name is None: name = origin.__name__ super().__init__(origin, inst=inst, name=name) self._nparams = nparams + self._defaults = defaults if origin.__module__ == 'builtins': self.__doc__ = f'A generic version of {origin.__qualname__}.' else: @@ -1594,12 +1595,22 @@ class _SpecialGenericAlias(_NotIterable, _BaseGenericAlias, _root=True): params = (params,) msg = "Parameters to generic types must be types." params = tuple(_type_check(p, msg) for p in params) + if (self._defaults + and len(params) < self._nparams + and len(params) + len(self._defaults) >= self._nparams + ): + params = (*params, *self._defaults[len(params) - self._nparams:]) actual_len = len(params) + if actual_len != self._nparams: + if self._defaults: + expected = f"at least {self._nparams - len(self._defaults)}" + else: + expected = str(self._nparams) if not self._nparams: raise TypeError(f"{self} is not a generic class") raise TypeError(f"Too {'many' if actual_len > self._nparams else 'few'} arguments for {self};" - f" actual {actual_len}, expected {self._nparams}") + f" actual {actual_len}, expected {expected}") return self.copy_with(params) def copy_with(self, params): @@ -2813,8 +2824,8 @@ DefaultDict = _alias(collections.defaultdict, 2, name='DefaultDict') OrderedDict = _alias(collections.OrderedDict, 2) Counter = _alias(collections.Counter, 1) ChainMap = _alias(collections.ChainMap, 2) -Generator = _alias(collections.abc.Generator, 3) -AsyncGenerator = _alias(collections.abc.AsyncGenerator, 2) +Generator = _alias(collections.abc.Generator, 3, defaults=(types.NoneType, types.NoneType)) +AsyncGenerator = _alias(collections.abc.AsyncGenerator, 2, defaults=(types.NoneType,)) Type = _alias(type, 1, inst=False, name='Type') Type.__doc__ = \ """Deprecated alias to builtins.type. diff --git a/Misc/NEWS.d/next/Library/2024-05-06-08-23-01.gh-issue-118648.OVA3jJ.rst b/Misc/NEWS.d/next/Library/2024-05-06-08-23-01.gh-issue-118648.OVA3jJ.rst new file mode 100644 index 0000000..7695fb0 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2024-05-06-08-23-01.gh-issue-118648.OVA3jJ.rst @@ -0,0 +1,2 @@ +Add type parameter defaults to :class:`typing.Generator` and +:class:`typing.AsyncGenerator`. |