如何组织一个可以作为__main__程序运行脚本的python模块？

Question

I'm starting a project in python, the code structure now as below:

project/
        __init__.py
        a.py
        b.py
        mainA.py
        utilities/
                   __init__.py
                   mainB.py
                   c.py

The __init__ files are all blank.

I want to run utilities/mainB.py as a program(using something like python main.py ), and mainB needs to import a.py and b.py . So I tried from .. import a and some other approaches, but the import failed. The error information is:

ValueError: Attempted relative import in non-package

So here comes the questions:

1. how to fix mainB.py so it can be run as a main program?
2. mainA.py can be run as main program now, it also imports a.py and b.py (using import a and import b ). I think the code structure may become more complex. Say, if mainA.py has to import a module from project/some/directory , how can I do that?

Answer 1

See this previous question . You have two options. One is to use the __package__ attribute as described in PEP 366 to set the relative name of your modules. The other is to execute your scripts as modules (using the -m flag to the interpreter) instead of running them directly as scripts.

Answer 2

You could use Python's built-in module-running functionality ( python -m <module> ).

python -m project.utilities.mainB

This allows you to write mainB normally as part of the package, so relative and absolute imports will both work correctly.

For an in-depth discussion of this functionality, see PEP-338 .

Answer 3

您应该在PYTHON_PATH中添加“ project”目录，然后在mainB.py中添加：

from project import a