oops, I meant GIL. I work with scientific computing. In my experience, the only justification I have of using other language (mostly C++) over python is to get over the interpreter lock, which over complicates your life if you want parallelisation. Multiprocessing is just awful, specially if you work with big chunks of data (I do mostly medical imaging). PyPy, even if it's faster, still has the same GIL constraints as CPython, so not really a big advantage IMO.