Python's int/long unification was done in Python 2.2 (PEP 237). Which by the way, I think it's a great feature, even if it makes it slower. That is what Python is about after all: simplicity and ease of use over performance. If you really need the max performance possible, don't use Python.

As far as I knew, the only thing that changed in Python 3 was that they renamed the long type to int, and they also removed L suffix. But from your code seems that other things have changed as well and now two structures are used for short integers. Do you know when this happened exactly and why?