How to use multiple versions of Python without uninstallation

Question

I am faced with a unique situation, slightly trivial but painful.

I need to use Python 2.6.6 because NLTK is not ported to Python 3 (that\'s what I could gather).

Answer 1

This page has an implementation of collections.Counter that works for Python 2.6:

• http://code.activestate.com/recipes/576611/