对 Python 子子包感到困惑

Question

正如标题所说，我对子子包感到困惑。我的包结构如下：

draw \
    __init__.py

    base \
        __init__.py
        utils.py
        events.py
        master.py
        basegui.py

现在，draw.base.events 的第一行如下：

import draw.base.utils as _utils

而draw.base的第一行是：

from draw.base.events import Event, RenderEvent, InputEvent, MouseEvent, KeyboardEvent

只需使用 IDLE 检查代码中的 SyntaxErrors：

import draw.base as base

给出以下AttributeError：

Traceback (most recent call last):
  File "<pyshell#0>", line 1, in <module>
    import draw.base
  File "Z:\Eigene Dateien\Eigene Dokumente\Python\draw\base\__init__.py", line 4, in <module>
    import draw.base.events as events
  File "Z:\Eigene Dateien\Eigene Dokumente\Python\draw\base\events.py", line 10, in <module>
    import draw.base.utils  as _utils
AttributeError: 'module' object has no attribute 'base'

谁能给我解释一下是什么问题？

Answer 1

为了在draw.base.events 中导入draw.base.utils，Python 需要导入现在正在导入的draw.base，所以还没有draw.base。您可以在draw.base.events 中将import draw.base.utils 替换为import utils（您也可以在2.7、3.x 中使用from ..base import utils 或from __future__ import absolute_import）来打破循环。