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Python 3.9包含PEP 585并弃用了typing模块中的许多类型，转而collections.abc支持__class_getitem__. 例如 就是这种情况Callable。对我来说，这似乎typing.Callable并且collections.abc.Callable应该始终表现得相似，但事实并非如此。

这个简单的示例会导致错误：

>>> from typing import Optional
>>> from collections.abc import Callable
>>> def foo(arg: Optional[Callable[[int], int]]) -> None:
...    pass
...
Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "/usr/local/lib/python3.9/typing.py", line 262, in inner
    return func(*args, **kwds)
  File "/usr/local/lib/python3.9/typing.py", line 339, in __getitem__
    return self._getitem(self, parameters)
  File "/usr/local/lib/python3.9/typing.py", line 463, in Optional
    return Union[arg, type(None)]
  File "/usr/local/lib/python3.9/typing.py", line 262, in inner
    return func(*args, **kwds)
  File "/usr/local/lib/python3.9/typing.py", line 339, in __getitem__
    return self._getitem(self, parameters)
  File "/usr/local/lib/python3.9/typing.py", line 451, in Union
    parameters = _remove_dups_flatten(parameters)
  File "/usr/local/lib/python3.9/typing.py", line 231, in _remove_dups_flatten
    return tuple(_deduplicate(params))
  File "/usr/local/lib/python3.9/typing.py", line 205, in _deduplicate
    all_params = set(params)
TypeError: unhashable type: 'list'

但同样的错误不会发生typing.Callable：

>>> from typing import Callable
>>> def foo(arg: Optional[Callable[[int], int]]) -> None:
...    pass
...
>>> # no error

如果稍微简化签名，也不会发生错误：

>>> from collections.abc import Callable
>>> def foo(arg: Optional[Callable[..., int]]) -> None:
...    pass
...
>>> # no error
>>> def foo(arg: Callable[[int], int]) -> None:
...    pass
...
>>> # no error

这是 Python 3.9 和 3.9.1 中的错误吗？

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1 回答 1

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是的，collections.abc.Callable不适用于 3.9.0 和 3.9.1 中的打字目的。它在此处报告并在3.9.2和 3.10中修复。在此期间您可以继续使用typing.Callable.

于 2021-01-23T11:17:04.557 回答