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我查看了 asyncio 包的__init__.py文件（在 Python 3.4.1 中）并偶然发现了最后几行：

"""The asyncio package, tracking PEP 3156."""

import sys

# The selectors module is in the stdlib in Python 3.4 but not in 3.3.
# Do this first, so the other submodules can use "from . import selectors".
# Prefer asyncio/selectors.py over the stdlib one, as ours may be newer.
try:
    from . import selectors
except ImportError:
    import selectors  # Will also be exported.

if sys.platform == 'win32':
    # Similar thing for _overlapped.
    try:
        from . import _overlapped
    except ImportError:
        import _overlapped  # Will also be exported.

# This relies on each of the submodules having an __all__ variable.
from .events import *
from .futures import *
from .locks import *
from .protocols import *
from .queues import *
from .streams import *
from .subprocess import *
from .tasks import *
from .transports import *

if sys.platform == 'win32':  # pragma: no cover
    from .windows_events import *
else:
    from .unix_events import *  # pragma: no cover


__all__ = (events.__all__ +
           futures.__all__ +
           locks.__all__ +
           protocols.__all__ +
           queues.__all__ +
           streams.__all__ +
           subprocess.__all__ +
           tasks.__all__ +
           transports.__all__)

考虑到上面的陈述，当这些名称实际上甚至不应该存在时，他们怎么可能访问events所有其他子模块（及其各自的变量）？据我所见，标准库的目录不是其中的一部分，子模块本身也没有定义变量。__all__from … import *asyncio/sys.pathsubmodule.__all__

附带说明：通过查看__init__.py文件，我真正想知道的是如何将所有子模块的名称自动添加到__all__我的包列表中，__init__.py而不是仅仅重复所有这些名称（因为它在几个标准库的其他包）。我目前的方法如下——也许你的答案会揭示这个asyncio包是如何成功实现这个看起来更像 Python 的把戏的。

from submodule1 import * # does not import __all__
from submodule1 import __all__ as submodule1_all
from submodule2 import *
from submodule2 import __all__ as submodule2_all

__all__ = submodule1_all + submodule2_all
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