Settings file reference is not found

I'm working on migrating an exsting Python 2.7 project to Python 3.9. I'm facing a directory structure-related issue in Python 3.

My current project directory structure is:

├───project
│   ├───core
|       +--__init__.py
|       +--main.py
|       +--settings.py
│   ├───jobs
|       +--job.py

main.py:

import settings


class Main:
    def __init__(self, a=None, b=settings.B):
        self.a = a
        self.b = b

    def start(self):
        print(self.a, self.b)

job.py:

import sys
# sys.path.insert(0, '../core/')
from core.main import Main
from core import settings

main = Main(settings.A)
main.start()

There is no issues with this structure when Python 2.7 interpreter is used, but in Python 3.9 I see the following error when job.py is executed:

  File "project\core\main.py", line 1, in <module>
    import settings
ModuleNotFoundError: No module named 'settings'

The issue is fixable by uncommenting the code on line #2 of the job.py script, but I would like to avoid hardcoding folder values like that. I would appreciate if someone could provide an alternative approach and an explanation why it's behaving this way in the newer Python version.

Due to ambiguity absolute import was removed in python3 for such use case. (This explains it very well: Changes in import statement python3)

You can use relative import for this use case maybe - https://docs.python.org/3/reference/import.html#package-relative-imports