python 2.x or 3.x
python, python-3.x
Solution
Python 2.6 and 2.7 have been written to ease the transition to Python 3. It will take some more time to port the more complex packages (i.e. those with many dependencies, or libraries written in C).
So if you are starting new projects, and all the libraries you need are there, it makes sense to start with 3.1. One of the more welcome changes is the handling of Unicode strings by default - it will prevent a lot of bugs.
But if you were to port a complete ERP application, or anything big, from 2.6 to 3.x, it could be a bloodbath right now. The unicode changes for instance are the hardest to apply from 2.x -> 3.x, and the low level C APIs have changed a lot as well.
Problem
Since there is a python 3.x, why don't we use it? Why do we still use 2.x? What's the difference?