What is "pypy"

PyPy is a Python interpreter and just-in-time compiler. PyPy focuses on speed, efficiency and compatibility with the original CPython interpreter.

PyPy started out being a Python interpreter written in the Python language itself. Current PyPy versions are translated from RPython to C code and compiled. The PyPy JIT (short for "Just In Time") compiler is capable of turning Python code into machine code at run time.