[pypy-dev] Use pypy if available otherwise fallback to CPython

[Dario Bertini]

I usually prepend my python scripts with

#! /usr/bin/env python

this way it'll resolve to your user's current python

by using it together with a virtualenv[1]

virtualenv --python=/path/to/pypy envname

you can have what you want, at least if you're in control of the deploy

I guess that if you'll just give the python script to someone who has
installed both pypy and cpython, you'd have to rely on some other
method

[1] http://pypi.python.org/pypi/virtualenv