I go between python, javascript, and c++ most weeks (not on the same project). I'm doing a little rust on the side just to learn it, same with haskell. I had a

I go between python, javascript, and c++ most weeks (not on the same project). I'm doing a little rust on the side just to learn it, same with haskell. I had a project in ocaml recently, but that probably won't happen again for a while. I find the biggest hassle working with multiple languages is trying to keep the libraries and data structure interfaces straight (i.e. push, extend, unshift, push_back, cons, :, ::, ...). Once I get into the language mindset the syntax itself doesn't seem to be much of a problem. I think I'm probably the most productive in python, mostly due to the huge ecosystem. I'm happiest when solving problems in haskell though, and increasingly I like rust (really hoping for higher-kinded types, which would put it in the running for my favorite).