出口装饰器，管理__all__ [英] Export decorator that manages __all__

问题描述

适当的Python模块会在称为__all__ public 符号>.管理该列表可能很乏味，因为您必须将每个符号列出两次.当然有更好的方法，可能使用装饰器，因此，人们只需将导出的符号注释为 @export .

A proper Python module will list all its public symbols in a list called __all__. Managing that list can be tedious, since you'll have to list each symbol twice. Surely there are better ways, probably using decorators so one would merely annotate the exported symbols as @export.

您将如何编写这样的装饰器?我敢肯定有不同的方法，所以我想看几个答案，并提供足够的信息，以便用户可以将这些方法相互比较.

How would you write such a decorator? I'm certain there are different ways, so I'd like to see several answers with enough information that users can compare the approaches against one another.

推荐答案

在中，使用装饰器?， Ed L 建议在实用程序库中包含以下内容:

In Is it a good practice to add names to __all__ using a decorator?, Ed L suggests the following, to be included in some utility library:

import sys

def export(fn):
    """Use a decorator to avoid retyping function/class names.

    * Based on an idea by Duncan Booth:
      http://groups.google.com/group/comp.lang.python/msg/11cbb03e09611b8a
    * Improved via a suggestion by Dave Angel:
      http://groups.google.com/group/comp.lang.python/msg/3d400fb22d8a42e1
    """
    mod = sys.modules[fn.__module__]
    if hasattr(mod, '__all__'):
        name = fn.__name__
        all_ = mod.__all__
        if name not in all_:
            all_.append(name)
    else:
        mod.__all__ = [fn.__name__]
    return fn

我们已经对名称进行了调整以匹配其他示例.在本地实用程序库中，只需编写

We've adapted the name to match the other examples. With this in a local utility library, you'd simply write

from .utility import export

，然后开始使用@export.只需一行惯用的Python，您将比这简单得多.不利的一面是，该模块确实需要使用__module__属性和sys.modules缓存来访问该模块，这两个 在某些更深奥的设置中可能会出现问题(例如自定义导入)机械，或包装其他模块中的功能以在此模块中创建功能.

and then start using @export. Just one line of idiomatic Python, you can't get much simpler than this. On the downside, the module does require access to the module by using the __module__ property and the sys.modules cache, both of which may be problematic in some of the more esoteric setups (like custom import machinery, or wrapping functions from another module to create functions in this module).

在公共 Barry Warsaw 的> package 与此类似.它也提供了一些基于关键字的语法，但是decorator变体依赖于上面使用的相同模式.

The python part of the atpublic package by Barry Warsaw does something similar to this. It offers some keyword-based syntax, too, but the decorator variant relies on the same patterns used above.

这个好答案由

This great answer by Aaron Hall suggests something very similar, with two more lines of code as it doesn't use __dict__.setdefault. It might be preferable if manipulating the module __dict__ is problematic for some reason.

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