How to import a file from another folder in a package

My project structure looks like this

pythonProject
|
|-__init__.py
|
|- a 
|  |- file_a.py 
|  |-__init__.py
|
|- b 
   |- file_b.py 
   |-__init__.py

I've also attached the image of my project's structure below.

enter image description here

My file_a.py looks like:

class class_a:
    def __init__(self):
        pass
    def show(self):
        print('class A')
if __name__ == "__main__":
    pass

My file_b.py looks like:

from pythonProject.a.file_a import class_a
class class_b:
    def __init__(self):
        pass
    def show(self):
        a = class_a()
        a.show()
if __name__ == "__main__":
    b = class_b()

But I keep getting an error No module named 'pythonProject'. All the folders do have __init__.py file. What am I doing wrong?

On the terminal, I run the command python b/file_b.py from inside the pythonProject.

Also, I would not like to add project path using sys library.

Thanks.

Things I've tried.

1. I added all the __init__.py file in all the folders. But all of them are empty. Should they have any specific references?
2. I tried the import line to ..a.file_a import class_a. Then I get the error: ImportError: attempted relative import with no known parent package
3. I tried the import line to a.file_a import class_a but then the error is ModuleNotFoundError: No module named 'a'.

I think the problem appears to be with your if __name__ == "main" condition in files a.py and b.py. Instead of "main", the correct string is "__main__" (double underscores on each side)

Change the condition in both files to if __name__ == "__main__": and try running file b.py again. This should resolve the error

> No module named 'pythonProject'.

In terms of imports, you can import class a from file a.py using the absolute import syntax in file b.py

from pythonProject.a.file_a import class_a

As long as you run file b.py from within the pythonProject directory, this should work.