Python PEP8 –?import not at the top of file with sys.path
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PEP8 –?import not at top of file with sys.path
提问by Luke Taylor
Problem
问题
PEP8 has a rule about putting imports at the top of a file:
PEP8 有一个关于将导入放在文件顶部的规则：
Imports are always put at the top of the file, just after any module comments and docstrings, and before module globals and constants.
导入总是放在文件的顶部，就在任何模块注释和文档字符串之后，以及模块全局变量和常量之前。
However, in certain cases, I might want to do something like:
但是，在某些情况下，我可能想要执行以下操作：
import sys
sys.path.insert("..", 0)
import my_module
In this case, the pep8command line utility flags my code:
在这种情况下，pep8命令行实用程序会标记我的代码：
E402 module level import not at top of file
E402 模块级导入不在文件顶部
What is the best way to achieve PEP8 compliance with sys.pathmodifications?
通过sys.path修改实现 PEP8 合规性的最佳方法是什么？
Why
为什么
I have this code because I'm following the project structuregiven in The Hitchhiker's Guide to Python.
我有这个代码是因为我遵循The Hitchhiker's Guide to Python 中给出的项目结构。
That guide suggests that I have a my_modulefolder, separate from a testsfolder, both of which are in the same directory. If I want to access my_modulefrom tests, I think I need to add ..to the sys.path
该指南建议我有一个my_module文件夹，与文件夹分开tests，两者都在同一目录中。如果我想访问my_modulefrom tests，我想我需要添加..到sys.path
采纳答案by Roland Smith
Often I have multiple files with tests in a subdirectory foo/testsof my project, while the modules I'm testing are in foo/src. To run the tests from foo/testswithout import errors I create a file foo/tests/pathmagic.pythat looks like this;
通常，我在foo/tests项目的子目录中有多个带有测试的文件，而我正在测试的模块在foo/src. 为了在foo/tests没有导入错误的情况下运行测试，我创建了一个如下所示的文件foo/tests/pathmagic.py；
"""Path hack to make tests work."""
import os
import sys
bp = os.path.dirname(os.path.realpath('.')).split(os.sep)
modpath = os.sep.join(bp + ['src'])
sys.path.insert(0, modpath)
In every test file, I then use
在每个测试文件中，我然后使用
import pathmagic # noqa
as the first import. The "noqa" comment prevents pycodestyle/pep8from complaining about an unused import.
作为第一个导入。"noqa" 注释可防止pycodestyle/pep8抱怨未使用的导入。
回答by astorga
If there are just a few imports, you can just ignore PEP8 on those importlines:
如果只有几个导入，您可以忽略这些import行上的 PEP8 ：
import sys
sys.path.insert("..", 0)
import my_module # noqa: E402
回答by Peuchele
There is another workaround.
还有另一种解决方法。
import sys
... all your other imports...
sys.path.insert("..", 0)
try:
import my_module
except:
raise
回答by Daniel Lee
Did you already try the following:
您是否已经尝试过以下操作：
import sys
from importlib import import_module
sys.path.insert("..", 0)
# import module
my_mod = import_module('my_module')
# get method or function from my_mod
my_method = getattr(my_mod , 'my_method')
回答by itsadok
I've just struggled with a similar question, and I think I found a slightly nicer solution than the accepted answer.
我刚刚在一个类似的问题上挣扎，我想我找到了一个比接受的答案更好的解决方案。
Create a pathmagicmodule that does the actual sys.path manipulation, but make the change within a context manager:
创建一个pathmagic执行实际 sys.path 操作的模块，但在上下文管理器中进行更改：
"""Path hack to make tests work."""
import os
import sys
class context:
def __enter__(self):
bp = os.path.dirname(os.path.realpath('.')).split(os.sep)
modpath = os.sep.join(bp + ['src'])
sys.path.insert(0, modpath)
def __exit__(self, *args):
pass
Then, in your test files (or wherever you need this), you do:
然后，在您的测试文件（或您需要的任何地方）中，您可以：
import pathmagic
with pathmagic.context():
import my_module
# ...
This way you don't get any complaints from flake8/pycodestyle, you don't need special comments, and the structure seems to make sense.
这样你就不会收到来自 flake8/pycodestyle 的任何抱怨，你不需要特别的注释，而且结构似乎是有道理的。
For extra neatness, consider actually reverting the path in the __exit__block, though this may cause problems with lazy imports (if you put the module code outside of the context), so maybe not worth the trouble.
为了更加整洁，请考虑实际恢复__exit__块中的路径，尽管这可能会导致延迟导入出现问题（如果您将模块代码放在上下文之外），因此可能不值得麻烦。
EDIT: Just saw a much simpler trick in an answer to a different question: add assert pathmagicunder your imports to avoid the noqacomment.
编辑：刚刚在另一个问题的答案中看到了一个更简单的技巧：assert pathmagic在您的导入下添加以避免noqa评论。
回答by Pierre Barre
To comply with the pep8, you should include your project path to the python path in order to perform relative / absolute imports.
为了符合 pep8，您应该将项目路径包含到 python 路径中，以便执行相对/绝对导入。
To do so, you can have a look at this answer: Permanently add a directory to PYTHONPATH
为此，您可以查看此答案：将目录永久添加到 PYTHONPATH
