Python, Circular Dependencies, And Singletons

I've dug myself into quite a hole here. I'm working on a Python/Kivy app in PyDev. The app runs off of many systems (about 10), so I shoved them into an engine to handle everything

Solution 1:

How about having a "registration" mechanism, where each system module "registers" itself with the Engine class using some module-level code:

engine.py

classEngine():
    @classmethoddefregister(cls, type):
        ...

system1.py

from engine import Engine

classSystem1():
    ...

Engine.register(System1)

That way, the Engine doesn't directly have to know what gets plugged into it.