Cannot import from a git submodule

Question

I'm having difficulties making a git submodule work.

I have a project ProjectA that basically is a mainA.py file and a subfolder with library files: The mainA.py contains a MainClass that is basically what should be called, and Libraries just contain scripts and classes for computations.

ProjectA/
    Libraries/
        __init__.py
        library1.py
        library2.py
    __init__.py
    mainA.py

In mainA.py I just do something like:

# content of mainA.py
from Libraries.library1 import ClassA, ClassB

class MainClass:
    # do stuff

if __name__ == '__main__':
    MainClass()

This just works fine, but I have now a ProjectB that needs to use the MainClass from ProjectA , so I decided to put ProjectA as a git submodule of ProjectB

git submodule add ProjectA_git_url

ProjectB/
    ProjectA/
    mainB.py
    .gitmodules

However now in mainB.py I'm trying to import MainClass from projectA .

# content of mainB.py
from ProjectA.mainA import MainClass

ModuleNotFoundError: No module named 'Libraries'

I think this happens because now Libraries is no longer hanging from the root directory, but inside the submodule ProjectA , so when mainA.py does:

from Libraries.library1 import ClassA, ClassB

The system cannot find Libraries . If I change mainA.py to do:

from ProjectA.Libraries.library1 import ClassA, ClassB

Then it works, but of course I don't want to change anything insise ProjectA , it is just a Project that should work either standalone or as a submodule of another project

What am I doing wrong? Is there a way to import MainClass from mainA.py when ProjectA is a submodule?

Answer 1

git is a development tool; you use it during development but not deployment. pip is a deployment tool; during development you use it to install necessary libraries; during deployment your users use it to install your package with dependencies.

Use submodules when you need something from a remote repository in your development environment. For example, if said remote repository contains Makefile(s) or other non-python files that you need and that usually aren't installed with pip .

That is, in your case you shouldn't make ProjectA a submodule of ProjectB , you should make ProjectA a Python dependency. Create packages for ProjectA and ProjectB and install them separately but allow ProjectB to import from ProjectA .

Dependencies are declared in setup.py or requirements.txt .

That said, if you insist on using submodules: either you have to manipulate sys.path yourself or you do relative import in mainA.py :

from .Libraries.library1 import ClassA, ClassB

Answer 2

将子模块路径添加到 mainB.py 中的系统路径假设您的子模块路径是“../ProjectB/ProjectA” sys.path.append(../ProjectB/ProjectA) 解决问题。