Lilypond + Python + Mac

[Lepsinasse]

Hello

I've been using lilypond for a while now, but I do have some problems with my
mac version. Everything was just fine until I install and uninstall apple
developper utilities. Now, when I launch lilypond, an error message pops up
telling me that lilypond finds no module named "os". I thought this module was a
python one, called with "from os import *", so I call the os module using python
in the terminal, and everything seems ok.
So my question is, is there a special path in whitch Lilyponds look for the
python utilities with an apple computer. I checked up my python files, and
everything seems ok.
Thanks