The big change was string/byte-array typing, which was a mess in Python 2 and was cleaned up in Python 3. And made worse in some cases (e.g. http://legacy.pyth

The big change was string/byte-array typing, which was a mess in Python 2 and was cleaned up in Python 3. And made worse in some cases (e.g. http://legacy.python.org/dev/peps/pep-0461/ http://legacy.python.org/dev/peps/pep-0461/). Even aside from that, I would argue that the benefits of cleaning up Unicode didn't come close to the cost of breaking everyone's code and fragmenting the language for 7+ years.