This Python library code converts between Lat/Long and UTM. I use it in Pygps, Mapview, and a few other programs. This same algorithm is available in libproj. There are python bindings for libproj in Thuban. Thuban is good, but I don’t want my code to depend on Thuban. Also turns out that there are independent Python bindings for proj.
You can download the current version.
Unpack it, and run “python setup.py install” as root. That will install it in your site-packages directory and byte-compile it.