Chaining sibling directory imports in Python 3.8+

In my Python project, I am having trouble with sibling directory imports. My file structure is as follows:

main_dir/
        __init__.py
        subdir1/
                __init__.py
                module1.py
                module2.py
        subdir2/
                __init__.py
                module3.py
        setup.py

Importantly, module1.py imports all the functions from module2.py, so in module1.py I have the following import:

from module2 import *

There are functions in module1.py that call functions from module2.py within them.

Running module1.py obviously works fine. The issue is that I need module3.py to import the functions from module1.py. To be very clear, in module3.py, I need to run a function from module1.py that calls a function from module2.py within it.

In other parts of my project, I have been struggling with importing sibling directories. A fix I found that has worked for Python 3.8.0-3.12.2 is to use a setup.py file and, in files that require a sibling import, use

import sys
sys.path.append('..')
from sibling_dir.module import needed_fun

This has been working, unlike any other solution I have tried such as

from ..sibling_dir.module import *

or from .. import siblingdir.module.

The setup.py file is as follows:

from setuptools import setup, find_packages

setup(name = 'example_name', version = '1.0', packages = find_packages())

(this of course requires the external setuptools package to be installed)

However, back to the main problem. I need module3.py to import functions from module1.py. In module3.py, I have tried the usual setup. Since module1.py imports functions from module2.py, I also import module2.py‘s functions:

In module3.py

import sys
sys.path.append('..')
from subdir1.module2 import *
from subdir1.module1 import *

I have also tried

import sys
sys.path.append('..')
import subdir1.module2
from subdir1.module1 import *

When I try to run module3.py, I get "No module named ‘module2’". This error occurs on the line from subdir1.module1 import *. I am wondering if there is some secret combination of imports to solve this problem, or a different approach entirely. This structure is important to my project, as organization will be very important as it gets larger. Furthermore, relative paths of some kind are essential, I cannot use absolute paths. One final thing that may matter is that none of the __init__.py‘s have anything in them, they are there primarily for setuptools to see those directories as packages (I think). I should also clarify that everything I try I have tried after running a fresh pip install . in the main_dir directory to utilize setuptools.py.

>Solution :

As long as the sibling folders are in a shared package, such as main_dir, you can import directly from there.

from main_dir.subdir1.module1 import *