python - 类型错误 : 'ABCMeta' object is not subscriptable on Callable

Question

我对 python 3.8 和 mypy 协同工作的方式有疑问。考虑这个代码:

from collections.abc import Callable

def feeder(get_next_item: Callable[[], str]) -> str:
    return get_next_item()

虽然 mypy 批准此代码，但使用 python 3.8 运行它会产生错误

Traceback (most recent call last):
  File "mypytest.py", line 3, in <module>
    def feeder(get_next_item: Callable[[], str]) -> str:
TypeError: 'ABCMeta' object is not subscriptable

所以，让我们试试别的:
from collections.abc import Callable

def feeder(get_next_item: Callable) -> str:
    return get_next_item()

此时python3.8会运行正常，但是mypy会说

mypytest.py:4: error: Returning Any from function declared to return "str"

除了在返回时使用 #type: ignore 之外，有没有办法摆脱这个陷阱？
提前致谢

Answer 1

谢谢XtianP。只是为了记录，这段代码对我来说效果很好

from typing import Callable

def feeder(get_next_item: Callable[[], str]) -> str:
    return get_next_item()

print( feeder(lambda : 'Hi man') )