为什么输入模块会导出“子模块”?

这个 typing 模块导出两个类, io re ,作为“伪子模块”,转载如下。通过给它们一个简单的例子,让它们看起来像模块的意图是什么 __all__ sys.modules ?

:所以 from typing import * 木卫一 和

但为什么要加 'typing.re' 和 'typing.io' 到 ?

typing.py :

import re as stdlib_re

# The pseudo-submodules 're' and 'io' are part of the public
# namespace, but excluded from __all__ because they might stomp on
# legitimate imports of those modules.

# ...

class io:
    """Wrapper namespace for IO generic classes."""

    __all__ = ['IO', 'TextIO', 'BinaryIO']
    IO = IO
    TextIO = TextIO
    BinaryIO = BinaryIO


io.__name__ = __name__ + '.io'
sys.modules[io.__name__] = io

Pattern = _alias(stdlib_re.Pattern, AnyStr)
Match = _alias(stdlib_re.Match, AnyStr)

class re:
    """Wrapper namespace for re type aliases."""

    __all__ = ['Pattern', 'Match']
    Pattern = Pattern
    Match = Match


re.__name__ = __name__ + '.re'
sys.modules[re.__name__] = re