The rule on the Python team side is:

- no API changes if the sub-minor version number is changed
- only API add if minor is changed
- anything possible if major changed

But as I got a very little feedback, it's very possible for me to forget something in the API: specialy with _Py_XXX() function, these functions with an '_' should not be used , normally... but in fact they are! some of them are event used in macros without '_' at start... so.

Anyway, for next releases of 2.x, I'll keep the compatibility, but I can't for the 3.x (dur to the rules explained on top of this post).