What's Python 3000/Python 3.0?
What changed in Python 3.0?
Read What's New in Python 3.0, which lists the changes between Python 2.6 and Python 3.0.
What will happen to the Python 2.x versions?
How should I port existing Python code to Python 3.0?
XXX describe 2to3.
One approach is to use 3.0's build_py_2to3 implementation of the build_py command. See Demo/distutils/test2to3.
You will have a single lib.py, written in 2.x. When you install in 3.0, lib2to3 will convert it to 3.x in the build area, and then install the 3.0 version.
That, of course, requires you to adjust lib.py in such a way that 2to3 will successfully and completely convert it. In two experiments, Martin von Loewis ported Django and Mark Hammond ported PythonWin to 3.0, and found that these adjustments were quite feasible. You look at what 2to3 does, find out what additional modifications need to be done, and apply them to the input of 2to3 so that
* 2to3 leaves these changes in place * they either have no effect or still work correctly when run in 2.x.
In this weblog posting, Guido van Rossum strongly suggests not changing your APIs when porting to 3.0, because API changes will make it difficult for users to tell whether test suite failures are due to the 2.6->3.0 transition or to the API changes.