3to2 is a project to convert cleaner 3.x code to 2.x.

3to2 started as a project idea to reuse the 2to3/lib2to3 codebase for
converting 3.x code to 2.x.  This creates a new package, 'refactor', which
supports lib2to3 and (non-existent) lib3to2.

The following goals were targeted at the US [[http://us.pycon.org|PyCon]] 2009 sprint of Python Core:

 *retain lib2to3 API since it is in use (perhaps deprecate it later)
 *build a base package 'refactor' and port lib2to3 to it
 *package refactor with a 3to2 script
 *tackle high-priority conversions

The discussions at the sprint pointed to a handful of essential conversions to
use as starting goals of 3to2:

 *from `__future__ import *` (2.6)
 *convert str or bytes to `u''` or `b''`, respectively
 *convert `print` functions (2.5 and earlier)
 *convert exceptions (2.5 and earlier)

How far back into 2.x should 3to2 go?

Conversions from 3.x to 2.4 and earlier have a lot more work to do than those
of 3.x to 2.6 and later.  `:-)`  During the sprint, we approached tackling major conversion items (see short list above) for 3.x to 2.6, then 2.5, then 2.4, ...

During the Google Summer of Code 2009, [[JoeAmenta|Joe Amenta]] wrote a more-or-less complete lib3to2.  It is hosted on [[http://bitbucket.org/amentajo/lib3to2|bitbucket]] and has a [[http://pypi.python.org/pypi/3to2|PyPI page]].