Source: 📖 Python Cookbook ch10.3 p399

Using relative imports

Rather than hardcoding a directory structure into your import statements which can make your code brittle if the structure changes, it is better to use import statements using ..

Assume we have the following tree structure:

project/
	__init__.py
	main.py
	A/
		__init__.py
		foo.py
	B/
		__init__.py
		bar.py
		spam.py

The spam.py module could import from the modules surrounding it by using the following code.

# project/B/spam.py

from . import bar

The dot is used to import from the same package (directory) that the current module exists in. To import from a package that exists on the same level as the current containing package, .. can be used.

# project/B/spam.py

from ..A import foo

The above code looks inside the A package for the foo.py module.

Relative import behaviour will only work when importing from proper python packages—directories inside which __init__.py has been declared. No code needs to be present inside __init__.py, it just has to exist inside the directory to establish it as a python package.