Depending on your needs, you may also want to check out the 2to3 library. It was written to automatically facilitate the conversion of Python 2.x apps to Python 3.0, so its main use case is taking one Python source file, performing some transformations on it, and then spitting out the result source file.
One benefit that lib2to3 has over the ast module is that ast does not preserve whitespace and comments, whereas lib2to3 does. If you're already dealing with autogenerated code this might not be a problem for you.
