PyPy is a fast, compliant alternative implementation of the Python language
(equivalent to CPython 2.7.1). It has several advantages and distinct
features:
Speed: thanks to its Just-in-Time compiler, Python programs often run
faster on PyPy.
Memory usage: large, memory-hungry Python programs might end up taking
less space than they do in CPython.
Compatibility: PyPy is highly compatible with existing python code. It
supports ctypes and can run popular python libraries like twisted
and django.
Sandboxing: PyPy provides the ability to run untrusted code in a fully
secure way.
Stackless: PyPy can be configured to run in stackless mode, providing
micro-threads for massive concurrency.
WWW: http://pypy.org/