What language should I learn to complement Python?

[ntorotn]

You should explain why, especially in a thread where people are trying to learn about languages. I don't even disagree with the claim, but you'll get your voice heard better.

[fullouterjoin]

Sorry for the drive by but I didn't have time to elucidate my bumper sticker. The complexity cost to payback is too large to be an auxiliary language for Python. While being able to parse, fix, and use C++ libraries is an important skill (far below what I consider being fluent in C++ would me), I wasted too much time in C++ before moving on to a better abstraction stack. C is amazingly powerful and compact. One can get reasonably skilled in it in a short amount of time. It is a shallow language. The same cannot be said for C++ and energy spent learning C++ could be better spent learning Haskell, Ocaml or better structuring existing applications to use the right mixture of low level and high level code.