Question on Bridging/Integration

Hi there,

I'm new the whole PyObjC thing and have a simple document-bases app for which my goal is to all the user (personal project, so actually just me :P) to provide his/her (my) own filtering logic on a per-document basis.

I basically have an NSSet of objects which need to be filtered based on a user-provided logic.
As the logic should not be limited to rather primitive NSPredicates I'd like to provide a barebones in-app Python editor in which the user can define his/her logic.

>From what I've found on the web so far I know that one can subclass one's own Objective-C classes from inside Python using "objc.lookUpClass(…)".
There is however still one question that remained unanswered:
Being able to instantiate an Objective-C object from Python is neat, but still isolated. How do I expose a particular object instance from one language to the other?
After all I need to pass my Objective-C object to Python for evaluation and receive an answer from it in respose. 

A minimal sample function (as provided by the user at runtime) would look something like this:

def shallRejectObject(object)
	if object.foo():
		return True
	return False

Being totally new to PyObjC I'm thinking of some kind of reverse "objc.lookUpClass(…)" to allow me to instantiate my Python subclass from within Objective-C. Or how else would one approach this?

Any hints?

Thanks in advance,
Vincent
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