I've found OCaml to be quite complementary to Python: It's excellent for functional programming and has one of the most sophisticated compile-time error checkin

I've found OCaml to be quite complementary to Python: It's excellent for functional programming and has one of the most sophisticated compile-time error checking systems I've ever used (two things relatively weak in Python). Both are very pragmatic and portable languages, as well. The OCaml community is tiny and rather quiet compared to Python's, though.