Sage is probably quite useful if you are a pure mathematician. The reason I couldn't use it is that it didn't behave well as a library, but they seem to have im

Sage is probably quite useful if you are a pure mathematician. The reason I couldn't use it is that it didn't behave well as a library, but they seem to have improved library support since then (http://www.sagemath.org/doc/tutorial/programming.html#section-standalone http://www.sagemath.org/doc/tutorial/programming.html#sectio...). But the project has definitely produced at least one A++ bit of code: Cython. That is very much worth learning and complementary to numpy (e.g. Cython/numpy integration: http://wiki.cython.org/tutorials/numpy http://wiki.cython.org/tutorials/numpy).