Python application extending, plugins

[John Pote]

Hi,

Has anyone any thoughts on structuring a program so that it can be extended 
simply and elegantly by a user who only has a compiled (.pyc) version of the 
application?

I wish to write an application, myApp, that provides a GUI to, amongst other 
things, a simulator implimented as a class. myApp's simulator may then be 
extended by more python code to produce what is effectively 'myApp2'. The 
simulator might then be further extended from myApp2 to myApp3 in a similar 
manor. Don't think there would be much call, if at all, to go beyond myApp3 
level. But who knows!

Any thoughts would be appreciated.

John Pote