PyPy is a Python implementation, alternative to the standard CPython. PyPy comes with a JIT (Just-in-Time compiler). We'll see the recent developments:
PyPy now supports either Python 2.7 or (in beta) Python 3.5.
Numpy and the scientific stack are getting ever closer to fully working.
We will also mention a potential future direction: getting rid of the GIL (Global Interpreter Lock). The Python community has been discussing removing the GIL for a long time, with no success so far. Targeting PyPy instead of CPython would still be quite involved, but more doable.