SymPy 1.0 Description:
SymPy is a Python library for symbolic mathematics. SymPy aims to become a full-featured computer algebra system (CAS) while keeping the code as simple as possible in order to be comprehensible and easily extensible. Moreover, SymPy is written entirely in Python and does not require any external libraries. The SymPy library is easy to install and get started with and it works everywhere, where Python 2.4 or newer is installed (Mac OS X, Linux, Windows, ...).