如何在开发时调试 python 模块

Question

Let's say we are developing a simple python module with the following directory structure

.
├── module
│   ├── __init__.py
│   ├── core.py
│   └── helpers.py
└── test.py

contents of init .py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

from .core import print_values

contents of core.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

from .helpers import values

def print_values():
    print(values)

if __name__ == '__main__':
    print_values()

contents of helpers.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

values = [0, 2, 6]

contents of test.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

from module import print_values
print_values()

now if we run python test.py with '.' as the working dir we get the expected output of [0, 2, 6] . Great!

So here is the problem, if we change the working dir to './modules' and run python3./core.py the following error will be raised:

ImportError: attempted relative import with no known parent package

So the question is how to design modules in a way that we can run python scripts from within it during development?

Answer 1

so the problem appears to be that relative imports coupled with the from keyword tries to import a __init__.py file.

In other words, the line

from .helpers import values 

tries to read./modules/helpers/ init .py, which does not exist. In order to make it work we change the import to:

if __name__ == '__main__':
    from helpers import values
else:
    from .helpers import values 

Note: since there are a lot of links on google that explain this problem from other use cases (using setup.py as possible solutions for example), i thought it would be a good idea to publish this specific case as i did not encounter it while searching for an answer.