package script cant find sibling script when executed from outside

[Gribouillis]

Unfortunately i get the error message: "no module named 'constant' "

According to your post, the module is named 'constants' and not 'constant'. Could this be the error?

You could try a relative import in function.py

from .constants import my_const

Note that 'relative' import means relative to the python packages hierarchy, not the file system's directories tree.