The General Multiprecision PYthon project (GMPY) focuses on Python-usable modules providing multiprecision arithmetic functionality to Python programmers.

Some informational text and '''old''' download files are at
http://gmpy.sourceforge.net/

The project has now moved to google-code:
http://code.google.com/p/gmpy

...which has been moved to GitHub:
https://github.com/aleaxit/gmpy

''GNU Multiple Precision Arithmetic Library http://gmplib.org''