I don't use Ruby very much, so I can't respond to the bulk of your comment, but I wanted to note that Dive Into Python was first written for Python 2.x, then rewritten for Python 3, not the other way around.
I didn't contradict your statement. Going by the discussions on this site on another thread, it seems that the Python 3 book is being backported. That only means that exercises/examples in the 3 book are being back-ported - perhaps they will be added to a new edition of the 2.x book.
http://en.wikipedia.org/wiki/Mark_Pilgrim#Dive_Into_Python