Python无法从包中导入模块 [英] Python can't import module from package

问题描述

我有一个Flask Restful项目，其布局如下(为方便起见，更改了文件名)

I have a flask restful project with the following layout (file names changed for convenience)

myproject/
    __init__.py
    app.py
    common/
        __init__.py
        util.py
    foo/
        __init__.py
        main.py
        utilities.py

foo/只是一个包含API端点之一的代码的文件夹，我计划将来添加其他端点，因此，我有common/util.py文件，其中包含将与其他API一起使用的可重用函数.端点.

foo/ is just a folder containing code for one of the API endpoints, I'm planning to add others in the future, for this reason I have common/util.py file which contains reusable functions that I will use with other API endpoints.

foo/main.py

foo/main.py

from flask_restful import Resource, request

from utilities import Analysis

class Foo(Resource):
    def get(self):      
        pass

在foo/utilities.py中，我的类带有一些获取数据的方法，我将这些类导入到foo/main.py中以返回JSON响应

in foo/utilities.py I have classes with methods that get some data, I import those classes to foo/main.py to return JSON response

类还使用了common/util.py中的某些函数，但是当我尝试将某些内容从common/util.py导入到foo/utilities.py时，我得到了import common.util ModuleNotFoundError: No module named 'common'

classes in foo/utilities.py also uses some functions from common/util.py but when I try to import something from common/util.py to foo/utilities.py I get import common.util ModuleNotFoundError: No module named 'common'

可能是什么原因造成的?我尝试导入各种方式: from common.util import my_func from .common.util import my_func from myproject.common.util import my_func

What could be causing this? I tried importing various ways: from common.util import my_func from .common.util import my_func from myproject.common.util import my_func

但无济于事.

这很重要，它是myproject/app.py:

from flask import Flask
from flask_restful import Api

from foo.main import Foo

app = Flask(__name__)
api = Api(app)

api.add_resource(Foo, '/Foo')

if __name__ == "__main__":
    app.run()

如果需要的话，我会在激活的virtualenv中进行所有操作

I'm doing all of this in activated virtualenv if it matters

推荐答案

从common.util导入my_func

from common.util import my_func

在Python 3中，这是绝对导入，也就是说，带有common/子目录的目录必须位于sys.path中.在您的情况下，这肯定是错误的方法.

In Python 3 this is an absolute import, that is, the directory with common/ subdirectory must be in sys.path. In your situation it's certainly a wrong approach.

从.common.util导入my_func

from .common.util import my_func

此导入期望common是foo的子目录，但情况并非如此.

This import expects common to be a subdirectory of foo which is also not the case.

从myproject.common.util导入my_func

from myproject.common.util import my_func

这最终是最好的方法，但要使其正常工作，myproject/子目录的父目录必须位于sys.path中.您可以安装整个myproject或将父目录添加到$PYTHONPATH环境变量，或者将目录添加到foo/main.py中的sys.path.像这样:

This is finally the best approach but for it to work the parent directory of myproject/ subdirectory must be in sys.path. Either you install the entire myproject or add the parent directory to $PYTHONPATH environment variable or add the directory to sys.path in foo/main.py. Something like:

PYTHONPATH=/home/to/parentdir /home/to/parentdir/myproject/foo/main.py

或

import sys
sys.path.insert(0, '/home/to/parentdir')

/home/to/parentdir是myproject/所在的目录.

在安装myproject或将其父目录添加到sys.path之后，您也可以使用相对导入.您需要记住，与foo相比，common是同级软件包，因此导入必须不是从.common而是从..common:

After installing myproject or adding its parent directory to sys.path you can also use relative import. You need to remember that common is a sibling package comparing to foo so the import must be not from .common but from ..common:

from ..common.util import my_func

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