Question

我看了一下asyncio软件包的__init__.py文件（在Python 3.4.1中），并且在最后几行中偶然发现：

"""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events语句，当这些名称实际上根本不存在时，他们如何能够访问__all__和所有其他子模块（及其各自的from … import *变量）？据我所知，标准库的asyncio/目录不是sys.path的一部分，子模块本身也没有定义submodule.__all__变量。

旁注：通过查看__init__.py文件我真正想知道的是我如何自动将所有子模块的名称添加到{{1我的包的列表__all__而不是只重复所有这些名称（因为它是在标准库的其他几个包中完成的）。我目前的方法如下 - 也许你的答案将揭示__init__.py包如何设法推出更具pythonic外观的技巧。

asyncio

Python标准库代码中的范围：如何存在这些变量？

0 个答案: