I have a module named extended.py which contains the following line:
from .basic import BasicModule
and the file basic.p
Relative imports only work for packages, but when you importing in extended.py you are running a top-level module instead.
The current directory may hold a __init__.py file but that doesn't make exended.py part of a package yet.
For something to be considered a package, you need to import the directory name instead. The following would work:
main.py
packagename\
__init__.py
basic.py
extended.py
then in main.py put:
import packagename.extended
and only then is extended part of a package and do relative imports work.
The relative import now has something to be relative to, the packagename parent.