Bear in mind that the original question is 'Should I learn C++ or Python?' This suggests the asker already knows C and is looking for the next step. Given that, w.r.t. to Lisp, I believe an ML-family language like OCaml would be a strict superset of the learning offered by a Lisp, and w.r.t. Haskell--hard core type fundamentalism rarely appeals to people trying to decide between C++ and Python.
I suggested OCaml for its static typing features, speed (comparable to C++), potential to deploy universally (desktop, mobile, web), and last but not least because of its pragmatism--if you need to do some imperative programming, it gets out of your way.
