Like Joshua, I would like to invite you to take a look on Umit. Umit
also have a parser for Nmap XML Output. I talked to fyodor about your
project, and we believe that would be great to have you working with
us on improving the xml parsing and other related stuffs on Umit.
Maybe, you could gather your efforts with ours, and we can have a
stronger tool that everyone can take advantage of. If you like the
idea, we could make some brainstorming here to see what people are
looking for at Umit and that it lacks until now and that you could
help with you XML and Python experience. Also, I can create a branch
for you at Umit repo, and add you account as umit developer at
sourceforge.
Let me know if you liked the idea!