I have a Flask project with this structure:

folderA/
    __init__.py
    subfolderA/
        __init__.py
        file.py
    run.py
    db.py

and in file.py I have this import: from folderA.db import method

when I run this app with “flask –app run –debug run”, the application starts with no problems. However when I try to start the project with another hosting server technique (I’m using Waitress for example) I get the following error: “No module named ‘folderA'”.

I even tried and ran the python file directly with py run.py (Within the folderA directory) I still get the same error.

My problem is that, why python interpreter does not understand that there is a init.py file in folderA, and why it does not recognise that folderA is a package?

Thanks for your help in advance.