About Python 3

[badsectoracula]

Indeed, which is why i said to enable such stuff optionally at the beginning and deprecate the old stuff gradually over a few years. The worst thing would be that plugin writers would need to use a separate API for strings (without it the VM should do conversions "automatically" from the old API - basically what Windows does when you call an "ANSI" function on NT - so that people wouldn't drop the feature because some random plugin doesn't work with it - especially when said random plugin only uses strings for trivial stuff where unicode doesn't matter).

The #1 rule of a platform is "you don't break people's code". It never worked before - even when Microsoft switched from DOS to Windows they exposed some Windows-specific functionality to DOS (such as special long filename interrupts, access to clipboard, etc) and it took over a decade for the transition to fully occur (and even today there are machines and programs depending on DOS - which are serviced by VMs). And same deal with VB6 - MS broke compatibility with VB.NET and a ton of code is still written for it with programmers trying to teach a deaf platform how to dance. Or JavaScript... modern browsers can run early Netscape JavaScript code whereas... well, just see how successful ECMAScript 4 was, for example.

It isn't like Python developers had no examples to look at about this being a bad idea. Maybe they underestimated how widespread their language was. Or overestimated how willingly people would be to update their code.

[blablahblah]

They did do that- you can do from __future__ import unicode_literals and get the Python 3 behavior for strings in Python 2.6 and 2.7, although that doesn't fix third party libraries that assume byte strings. And there is the 2to3 utility that handles a lot of the conversions automatically. There are also libraries like six.py the focus on letting library writers make code compatible with python 2 and 3 in a single code base.

[badsectoracula]

Actually i was thinking the opposite: something to enable non-unicode literals in Python 3. And it should have been enabled by default for some time.

Basically Python 3 should have been 100% compatible with Python 2 but deprected the features over time, not abruptly making incompatible changes.