The important part of Python 3 is the bytes/str/unicode rework, and there’s no way to make that not a breaking change. Everything else is minor stuff that’s all

The important part of Python 3 is the bytes/str/unicode rework, and there’s no way to make that not a breaking change. Everything else is minor stuff that’s allowed to be breaking because the str change already broke backwards compatibility. (And yes, making strings text rather than bytes was really that important. Python 3 would be a huge improvement even if it were only that and some other safety things like removing the default ordering of incompatible types.)