__subclasses__ not showing anything

Question

I'm implementing a function that returns an object from the appropriate subclass. If I move SubClass from base.py, no subclasses appear for __subclasses__. Are they required to be in the same file? Perhaps the fact that I'm never importing directly subclass.py hides the subclass from python? What can I do? I have even checked the attribute __mro__ and get_subclass points to the right class.

# project/main.py
from project.src.base import get_subclass

obj = get_subclass(cls,name) # Returns an object of a subclass of cls

# project/src/subclass.py
from project.src.base import BaseClass

class SubClass(BaseClass):
    pass

# project/src/base.py
def get_subclass(cls,name):
    subclss = cls.__subclasses__ # This is returning an empty list
    pass

class BaseClass(object):
    pass

Answer 1

Python only runs code of modules that are imported. If you move code to a different module but never import it, Python does not know about its contents.

You have to import the files containing the subclasses you want accessible.

# project/src/__init__.py
import project.src.base      # executes the ``BaseClass`` definition
import project.src.subclass  # executes the ``SubClass`` definition

Note that it does not really matter where you import these - they must be imported before you need SubClass to appear in __subclasses__, though.