Import error when trying to import python module from other folder

December 24, 2022

This is my project structure:

/my_project
    /first_folder
        first.py
    /second_folder
        second.py

second.py

def hello():
    print('hello')

first.py

from ..second_folder import second

second.hello()

when i run first.py i get the following error:

ImportError: attempted relative import with no known parent package

How can I avoid this problem?

>Solution :

Normally when you run your script as the main module, you shouldn’t use relative imports in it. That’s because how Python resolves relative imports (using __package__ variable and so on…)

This is also documented here:

Note that relative imports are based on the name of the current
module. Since the name of the main module is always "__main__",
modules intended for use as the main module of a Python application
must always use absolute imports.

There are ways to make this work for example by hacking __package__, using -m flag, add some path to sys.path(where Python looks for modules) but the simplest and general solution is to always use absolute imports in your main script.

When you run a script, Python automatically adds the directory of your script to the sys.path, which means anything inside that directory (here first_folder is recognizable by interpreter. But your second_folder is not in that directory, you need to add the path to the my_project(which has the second_folder directory) for that.

Change your first.py to:

import sys

sys.path.insert(0, "PATH TO /my_project")

from second_folder import second

second.hello()

This way you can easily go into first_folder directory and run your script like: python first.py.

Final words: With absolute imports, you don’t have much complexity. Only think about "where you are" and "which paths are exists in the sys.path".