In short, this is far trickier than you might imagine.
It's come up a number of times on the Python / Python-win32
lists. A recent thread is here:
http://mail.python.org/pipermail/python-list/2009-May/713077.html
But if you simply Google for things like:
site:mail.python.org sysinternals handle
You'll get a bunch of hits asking / answering the same thing.
TJG