PyPy is a fast, compliant alternative implementation of the Python language
(2.7.2). 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.
 - As well as other features.

WWW: http://pypy.org/