[tdicola]

I really wish there was more thought put into allowing code to be compatible with both Python 2 and 3. The fact that the six library (which supports writing Python 2 and 3 compatible code) isn't in the core Python library is a big fail IMHO.

I've written a few things that are meant to support Python 2 and 3 from the same codebase and it was a bit of a nightmare finding all of the gotchas. Stupid little stuff like changing dict.iteritems() and replacing it with dict.items() (which still exists in Python 2 but doesn't do what you expect!) in 3 are a big pain to deal with when writing code that has to work with python 2 and 3.

This page has a lot of good advice, but the fact it's so long is just a testament to how painful the 2 to 3 transition is for people: http://python-future.org/compatible_idioms.html