PyQuante is an open-source suite of programs for developing quantum chemistry
methods. The program is written in the Python programming language, but has
many "rate-determining" modules also written in C for speed. The resulting
code, though not as fast as Jaguar, NWChem, Gaussian, or GAMESS, is much
easier to understand and modify. The goal of this software is not necessarily
to provide a working quantum chemistry program (although it will hopefully do
that), but rather to provide a well-engineered set of tools so that scientists
can construct their own quantum chemistry programs without going through the
tedium of having to write every low-level routine.