> If there's one lesson we've learned from the Python 2 to 3 transition, it's that it would have been very beneficial if Python 2 and 3 code could coexist in th

> If there's one lesson we've learned from the Python 2 to 3 transition, it's that it would have been very beneficial if Python 2 and 3 code could coexist in the same Python interpreter. We blew it that time, and it set us back by about a decade. A very characteristic thing for a core Python developer to say: it's stupid, baseless, but gets a standing ovation. The reason Python 3 wasn't catching up is because it offered no tangible benefits. Had it been, say, 10x faster than Python 2, then there would've been a reason. Had it offered sensible concurrency, there would've been a reason, had it offered some way to automatically verify programs... or a bunch of other useful things you might expect from a language, there would've been a reason to switch. But Python 3 was and still is a worthless change. It just gives you the ability to do the same things you could already do but in a slightly different way. If CPython project didn't refuse to support Python 2, it would be still alive and well. I've lived for a while with the language that had to support two versions at the same time: ActionScript. After AS3 was released, the SWF format and Flash player had changed to support executing both at the same time. The cases when both were used at the same time were very rare. They were never a part of an upgrade process -- usually it was because someone had to embed code they were under contractual obligation to execute (s.a. showing ads). Nobody partially upgraded their projects. Now, even though Python didn't provide a way to run two versions of the language at the same time, it wouldn't have been hard to do on your own, if you really wanted that: say modify the multiprocessing module to launch Python 2 from Python 3 or Python 3 from Python 2. Or create a native module embedding a Python interpreter of a different version. There are other ways as well... but nobody was doing that. Nobody needed that. There's no evidence anyone wanted to run both versions of Python at the same time, but, instead of facing the music and understanding that Python 3 wasn't wanted, these people will pet themselves on the back, tell each other how great their project is, and how it doesn't succeed for any other reason beside them being incompetent.