为什么此函数类型注释不正确（错误：泛型类型缺少类型参数）？

Question

此函数类型注释是否正确？

import subprocess
from os import PathLike
from typing import Union, Sequence, Any


def run(shell_command: Union[bytes, str, Sequence[Union[bytes, str, PathLike]]], **subprocess_run_kwargs: Any) -> int:
    return subprocess.run(shell_command, check=True, shell=True, **subprocess_run_kwargs).returncode

我猜不是，因为我得到：

he\other.py:6: error: Missing type parameters for generic type

要得到同样的错误，然后将上面的代码保存在 中other.py，然后：

$ pip install mypy

$ mypy --strict other.py

Answer 1

如 sanyash 的回答中所述，os.PathLike被定义为泛型类型。您可以查看typeshed repo中的存根。但是，os.PathLike仅在存根文件中是通用的，可导入的实现os不是.

不指定类型 var 参数 ( path: PathLike) 会导致 mypy 错误。指定类型 var 参数 ( path: PathLike[Any]) 会导致 Python 解释器（运行时）错误。

这个确切的问题已在 mypy 存储库中作为#5667 提出。因此PR #5833扩展了 mypy 文档：

• https://mypy.readthedocs.io/en/latest/runtime_troubles.html#using-classes-that-are-generic-in-stubs-but-not-at-runtime

添加的部分指出了三种处理方法：

1. 可以通过特殊from __future__ import annotations导入禁用 Python 解释器（在运行时）对注释的解释，请参见此处。这计划成为 Python 3.10 中的默认设置，并解决一堆与注释相关的问题。

   from __future__ import annotations
   from os import PathLike
   import subprocess
   from typing import Any, Sequence, Union
   
   def run(shell_command: Union[bytes, str, Sequence[Union[bytes, str, PathLike[Any]]]], **subprocess_run_kwargs: Any) -> int:
        return subprocess.run(shell_command, check=True, shell=True, **subprocess_run_kwargs).returncode
   

2. 使用typing.TYPE_CHECKING依赖于类型检查或Python解释（运行时）是否解释该文件以提供不同的注释。

   from os import PathLike
   import subprocess
   from typing import Any, Sequence, TYPE_CHECKING, Union
   
   if TYPE_CHECKING:
       BasePathLike = PathLike[Any]
   else:
       BasePathLike = PathLike
   
   def run(shell_command: Union[bytes, str, Sequence[Union[bytes, str, BasePathLike]]], **subprocess_run_kwargs: Any) -> int:
       return subprocess.run(shell_command, check=True, shell=True, **subprocess_run_kwargs).returncode
   

3. 以字符串形式提供注释。Python 解释器（运行时）不会解释注释，但 mypy 会获取正确的含义。

   import subprocess
   from typing import Any, Sequence, Union
   
   def run(shell_command: Union[bytes, str, Sequence[Union[bytes, str, 'PathLike[Any]']]], **subprocess_run_kwargs: Any) -> int:
       return subprocess.run(shell_command, check=True, shell=True, **subprocess_run_kwargs).returncode
   

Answer 2

PathLike是泛型类型，因此您需要将其与类型参数一起使用（AnyStr例如）：

import subprocess
from os import PathLike
from typing import Union, Sequence, Any, AnyStr


def run(shell_command: Union[bytes, str, Sequence[Union[bytes, str, PathLike[AnyStr]]]], **subprocess_run_kwargs: Any) -> int:
    return subprocess.run(shell_command, check=True, shell=True, **subprocess_run_kwargs).returncode

相关问题：

• https://github.com/python/mypy/issues/6112
• https://github.com/python/mypy/issues/6128

更新

抱歉，我没有在运行时检查这段代码。通过一些技巧，可以编写一个解决方法：

import subprocess
from os import PathLike as BasePathLike
from typing import Union, Sequence, Any, AnyStr, TYPE_CHECKING
import abc


if TYPE_CHECKING:
    PathLike = BasePathLike
else:
    class FakeGenericMeta(abc.ABCMeta):
        def __getitem__(self, item):
            return self

    class PathLike(BasePathLike, metaclass=FakeGenericMeta):
        pass

def run(shell_command: Union[bytes, str, Sequence[Union[bytes, str, PathLike[AnyStr]]]], **subprocess_run_kwargs: Any) -> int:
    return subprocess.run(shell_command, check=True, shell=True, **subprocess_run_kwargs).returncode

与此解决方法相关的问题：

• mypy：如何定义通用子类
• https://github.com/python/mypy/issues/5264