The future source tree includes scripts called futurize and pasteurize to aid in making Python 2 code or Python 3 code compatible with both platforms (Py2/3) using the :mod:`future` module. These are based on lib2to3 and use fixers from 2to3, 3to2, and python-modernize.

futurize passes Python 2 code through all the appropriate fixers to turn it into valid Python 3 code, and then adds __future__ and future package imports.

For conversions from Python 3 code to Py2/3, use the pasteurize script instead. This converts Py3-only constructs (e.g. new metaclass syntax) and adds __future__ and future imports to the top of each module.

In both cases, the result should be relatively clean Py3-style code that runs mostly unchanged on both Python 2 and Python 3.