如何在Python 3中使这些相对导入工作？ [英] How do I make these relative imports work in Python 3?

问题描述

我的目录结构如下所示：

I have a directory structure that looks like this:

project/
        __init__.py
        foo/
            __init.py__
            first.py
            second.py
            third.py
        plum.py

在项目/ foo / __ init __。py 我从 first.py导入类， second.py 和 third.py 并将它们放入 __ all __ 。

In project/foo/__init__.py I import classes from first.py, second.py and third.py and put them in __all__.

中有一个类first.py 名为 WonderfulThing 我想在 second.py 中使用，并希望通过导入 *进行导入来自 foo 。 （这个问题的范围超出了我为什么要这样做，假设我有充分的理由。）

There's a class in first.py named WonderfulThing which I'd like to use in second.py, and want to import by importing * from foo. (It's outside of the scope of this question why I'd like to do so, assume I have a good reason.)

在秒。 py 我尝试过来自.foo import * ，来自foo import * 和来自。 import * 并且在这些情况下都没有导入 WonderfulThing 。我还尝试了来自..foo import * 的，这会引发错误尝试相对导入超出toplevel包。

In second.py I've tried from .foo import *, from foo import * and from . import * and in none of these cases is WonderfulThing imported. I also tried from ..foo import *, which raises an error "Attempted relative import beyond toplevel package".

我已经阅读了文档和PEP，我无法弄清楚如何使这项工作。任何帮助将不胜感激。

I've read the docs and the PEP, and I can't work out how to make this work. Any assistance would be appreciated.

澄清/编辑：似乎我可能误解了 __ all __ <的方式/ code>在包中工作。我使用它和模块一样，

Clarification/ It seems like I may have been misunderstanding the way __all__ works in packages. I was using it the same as in modules,

from .first import WonderfulThing
__all__ = [ "WonderfulThing" ]

但再次查看文档似乎建议 __ all __ 只能在包中使用，以指定默认导入的模块的名称;似乎没有任何方法可以包含任何不是模块的东西。

but looking at the docs again it seems to suggest that __all__ may only be used in packages to specify the names of modules to be imported by default; there doesn't seem to be any way to include anything that's not a module.

这是正确的吗？

编辑：非通配符导入失败（无法导入名称WonderfulThing ）。从中尝试。 import foo 失败，但 import foo 有效。不幸的是， dir（foo）什么都没有显示。

A non-wildcard import failed (cannot import name WonderfulThing). Trying from . import foo failed, but import foo works. Unfortunately, dir(foo) shows nothing.

推荐答案

编辑：我确实误解了这个问题：没有 __所有__ 并不仅限于模块。

I did misunderstand the question: No __all__ is not restricted to just modules.

一个问题是你想做什么相对进口。从project.foo import * 执行，这里没有任何问题。其次，对foo的 __ all __ 限制不会阻止你从project.foo.first导入导入WonderfulThing ，或者只需从.first导入WonderfulThing ，这仍然是最好的方式。

One question is why you want to do a relative import. There is nothing wrong with doing from project.foo import *, here. Secondly, the __all__ restriction on foo won't prevent you from doing from project.foo.first import WonderfulThing, or just from .first import WonderfulThing, which still will be the best way.

如果你真的想导入很多事情，最好从项目导入foo 做，然后使用 foo.WonderfulThing 而不是做 import * ，然后直接使用 WonderfulThing 。

And if you really want to import a a lot of things, it's probably best to do from project import foo, and then use the things with foo.WonderfulThing instead for doing an import * and then using WonderfulThing directly.

但是要回答您的直接问题，要从second.py中的 __ init __ 文件导入，请执行以下操作：

However to answer your direct question, to import from the __init__ file in second.py you do this:

from . import WonderfulThing

或

from . import *

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