ModuleNotFoundError: No module named – while importing a module from another folder

I am getting the famous – ModuleNotFoundError when I try to import a module from another folder. Here is the folder structure –

packages
   - packageA
     - src
       - packagename
         - app.py <-- imports the readers.reader_module
         - __init__.py
         - readers
           - __init__.py
           - reader_module.py <-- contains a read()
          

The source under packagename will be packaged and hence I have added __init__.py under it. Similarly, under readers folder __init__.py is added.

When I import reader_module in app.py I get – ModuleNotFoundError: No module named 'packagename'.

I tried below import statements inside app.py but no luck –

• from packagename.readers.reader_module import read
• from .readers.reader_module import read
• from readers.reader_module import read

I tried to simulate your example and I was able to import with syntax

from readers.reader_module import sum_nums