On the subject of PyPy, I'd never used it until a month or so ago but I've been working on reinforcement learning models for a final year computer engineering project and slow training times were a serious problem until I found I could get a 10x speed boost without changing a line of code simply by switching from the default Python interpreter to PyPy. (Average training time dropped instantly from three minutes per episode to twenty seconds.) I'm seriously impressed by the work the PyPy guys have done.