Python导入，路径，目录和模组 [英] Python Imports, Paths, Directories & Modules

问题描述

首先让我说，我在过去一周中进行了广泛的研究，但尚未找到这些问题的实际答案-只是一些模糊的答案，并不能真正解释正在发生的事情.如果仅是因为我错过了我想要的东西，对不起-请指向正确的方向.

Let me start by saying I've done extensive research over the course of the past week and have not yet found actual answers to these questions - just some fuzzy answers that don't really explain what is going on. If that's just cause I missed what I was looking for, I'm sorry - please just point me in the correct direction.

我的目录结构是:

TestProject/
    runtest*
    testpackage/
        __init__.py
        testmod.py
        testmod2.py
        testsubs/
            testsubmod.py

一些注意事项:

• 我正在Ubuntu上使用python2.7
• 我正在使用bpython进行测试
• 我正在从特定目录运行bpython以测试导入的行为
• 我正在尝试遵循最佳做法.
• 此软件包尚未安装，位于随机的dev目录中
• 此目录不在pythonpath中
• 我在软件包目录中只有一个 init .py
• 嵌套目录中没有 init .py文件
• init .py文件为空
• testpackage/testmod.py包含TestModClass
• testpackage/testsubs/testsubmod.py包含TestSubModClass

• I'm using python2.7 on Ubuntu
• I'm testing with bpython
• I'm running bpython from specific directories to test the way import behaves
• I'm attempting to follow best practices.
• This package is not installed, it's in a random dev directory
• This directory is not in the pythonpath
• I have a single init.py in the package directory
• There are no init.py files in the nested directories
• The init.py file is empty
• testpackage/testmod.py contains TestModClass
• testpackage/testsubs/testsubmod.py contains TestSubModClass

我观察到的事情

• 当我从TestProject运行bpython/导入testpackage 时有效
  • 这不会导入testpackage.testmod
  • 我根本无法访问testpackage.testmod
  • When I run bpython from TestProject/ import testpackage works
    • This does not import testpackage.testmod
    • I cannot access testpackage.testmod at all
    • 我认为这不是正确的方法，如果用户不想导入该模块怎么办?
    • 这样做非常好，这样我就可以用STL或扭曲的名称(例如testpackage.logging)来用重叠的名称命名自己的模块，而不会引起错误(不得不像customerlogging这样命名自己的模块，而不是像这样来命名自己的模块，而不是只是mypackage.logging)

    问题:

    1. Python处理软件包和&的导入时是否有所不同?尝试从当前目录导入时，pythonpath中是否存在模块?
    2. 为什么不导入testpackage可以让我访问testpackage.testmod?导入os后，便可以访问os.path(等).
    3. 对于软件包，我应该坚持在基本目录中使用单个 init .py，还是应将其嵌套在后续目录中?
    4. 如何导入指定软件包名称的模块? IE.从testmod.py，我想导入testpackage.testmod2，而不只是testmod2.
    5. 从subsubs目录导入子模块的正确方法是什么?
    1. Does python deal differently with imports on packages & modules that exist in the pythonpath than when you are trying to import from your current directory?
    2. Why doesn't import testpackage give me access to testpackage.testmod? When I import os, I can then access os.path (etc).
    3. With a package, should I stick to using a single init.py in the base directory, or should I be nesting them in subsequent directories?
    4. How can I import a module specifying the package name? I.E. from testmod.py, I would like to import testpackage.testmod2 rather than just testmod2.
    5. What is the proper way to import submodules from the subsubs directory?
    1. 我看到的唯一解决方案是将该目录添加到 init .py的pythonpath中，但是我不知道这是否正确.
    1. The only solution I see is to append that directory to the pythonpath from init.py, but I don't know if that's the correct way.

  谢谢.

  推荐答案

  首先，您将在 Python教程的第6节.

  (1)python处理软件包&的导入是否有所不同?尝试从当前目录导入时，pythonpath中是否存在模块?

  (1) Does python deal differently with imports on packages & modules that exist in the pythonpath than when you are trying to import from your current directory?

  不，不是.实际上，Python在导入模块时总是搜索sys.path.仅在sys.path包含具有空字符串的条目(即当前目录)的情况下，才能找到当前目录中的模块.

  No, it doesn't. Actually, Python always searches sys.path when importing modules. Modules in the current directory are only found since sys.path contains an entry with the empty string, meaning the current directory.

  (2)为什么import testpackage不能给我访问testpackage.testmod的权限?导入os时，然后可以访问os.path(等).

  (2) Why doesn't import testpackage give me access to testpackage.testmod? When I import os, I can then access os.path (etc).

  为了提高效率，import testpackage仅加载testpackage/__init__.py.如果需要testpackage.testmod，则必须明确导入它:

  For efficiency, import testpackage only loads testpackage/__init__.py. If you need testpackage.testmod, you have to explicitely import it:

  import testpackage   # Just imports testpackage, not testpackage.testmod!
  import testpackage.testmod   # Import *both* testpackage and testpackage.testmod!
  

  如果您始终要导出testmod，请在__init__.py中导入它，这就是os(os/__init__.py)的作用.这样，如果导入testpackage，则testpackage.testmod始终隐式可用.

  If you always want to export testmod, import it within __init__.py, this is what os (os/__init__.py) does. This way, testpackage.testmod is always available implicitely if you import testpackage.

  由于Python是跨平台的，实际上，由于某些文件系统不区分大小写，因此实际上没有办法在目录中自动一致地自动加载模块. Python不知道是否将os/path.py加载为os.path或os.Path等.

  Since Python is cross-platform, there is actually no way to consistently and automatically load modules in a directory, because some filesystems are case-insensitive (Windows!). Python would not know whether to load os/path.py as os.path or os.Path, etc.

  (3)使用软件包，我应该坚持在基本目录中使用单个__init__.py还是应该将它们嵌套在后续目录中?

  (3) With a package, should I stick to using a single __init__.py in the base directory, or should I be nesting them in subsequent directories?

  每个子软件包始终需要一个__init__.py.关于删除此要求的讨论，但决定保留原样.

  You always need an __init__.py for each subpackage. There were discussions on dropping this requirement, but it was decided to keep it as it is.

  (4)如何导入指定软件包名称的模块? IE.从testmod.py，我想导入testpackage.testmod2，而不只是testmod2.

  (4) How can I import a module specifying the package name? I.E. from testmod.py, I would like to import testpackage.testmod2 rather than just testmod2.

  这应该有效.只要确保您从顶级目录中运行代码即可.如果当前目录为testpackage，则testmod不知道它在软件包中.

  This should work. Just ensure that you run the code from the top-level directory. If the current directory is testpackage, testmod does not know that it's in a package.

  首选方法是使用相对的包内导入，但是:

  The preferred way is to use relative intra-package imports, though:

  from . import testmod2
  

  如果存在名为testmod2的全局模块，这可以防止名称冲突，并使您可以毫无问题地使用程序包中的知名模块的名称.

  This prevents name clashes if there is a global module named testmod2 and enables you to use the names of well-known modules within your package without problems.

  (5)从subsubs目录导入子模块的正确方法是什么? 我看到的唯一解决方案是将该目录附加到__init__.py的pythonpath中，但是我不知道这是否是正确的方法.

  (5) What is the proper way to import submodules from the subsubs directory? The only solution I see is to append that directory to the pythonpath from __init__.py, but I don't know if that's the correct way.

  不，不要那样做！绝对不要在其中一个父目录已经位于sys.path中时将目录放置到sys.path中！这可能会导致您的模块被加载两次，这是一件坏事！

  No, don't do that! Never, ever put a directory to sys.path when one of it's parent directories already is in sys.path! This could cause your modules to be loaded twice, which is a bad thing!

  通常，您应该能够使用绝对或相对导入方式从子包中加载模块:

  Usually you should be able to load modules from subpackages using absolute or relative imports:

  import testpackage.testsubs.testsubmod
  from testpackage.testsubs import testsubmod
  from .testsubs import testsubmod
  

  只需确保在testsubs/内创建一个__init__.py！

  Just make sure to create a __init__.py within testsubs/!

  这篇关于Python导入，路径，目录和模组的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！