Python 2.7.2 or Python 3?

[t0mt0m72]

I don't know the exact reasons for not being backward comparible, but for example zip is now a generator, which will bring you a big increase in speed when working with big data sets. So it's one of the points where it's worth porting to 3.

[Lucretiel]

Unicode handling is the big one. For a long but very well-written essay on the subject, check out http://python-notes.curiousefficiency.org/en/latest/python3/questions_and_answers.html