mpmath

Mpmath is a pure-Python library for arbitrary-precision floating-point arithmetic. It implements the standard functions from Python’s math and cmath modules (exp, log, sin, etc.), plus a few nonelementary special functions (gamma, zeta, etc.), and has utilities for arbitrary-precision numerical differentiation, integration, root-finding, and interval arithmetic. It supports unlimited exponent sizes, has full support for complex numbers, and offers better performance than Python’s standard decimal library. Mpmath is lightweight and easy to install or include in other software due to being written entirely in Python with no additional dependencies. (Source: http://freecode.com/)