A couple of notes...
MacPython is a project from before Mac OS X. Any new Mac comes with an Apple supplied distribution of Python. Just open a terminal and type python and you'll be in the interpreter.
Python for Cocoa is pretty interesting (I was already toying around with it earlier today) but be warned that Cocoa is very ObjectiveC-esqe and not very Python-esqe. Even being fairly familiar with both Cocoa and Python it was a bit mind-bending for me.
Though, you could get even more bizarre and go with Ruby/Cocoa and really blow your mind :P