Why Python3

[MRAB]

Terry Reedy wrote:
> Some people appear to not understand the purpose of Python3 or more 
> specifically, of the changes that break Python2 code. I attempt here to 
> give a relatively full explanation.
> 
> SUMMARY: Python3 completes (or makes progress in) several transitions 
> begun in Python2.
> 
> In particular, Python3 bunches together several feature removals (which 
> always break someone's code) and a few feature changes (which also break 
> code). The alternative would have been to make the same changes, a few 
> at a time, over several releases, starting with about 2.5.
> 
> Another alternative would have been to declare 2.0 or 2.1 complete at 
> far as it went and forbid adding new features that duplicate and 
> supersede existing features.
> 
> Another would have been to add but never remove anthing, with the 
> consequence that Python would become increasingly difficult to learn and 
> the interpreter increasingly difficult to maintain with volunteers. I 
> think 2.7 is far enough in that direction.
> 
[snip]
It's clear that Guido's time machine is limited in how far it can travel
in time, because if it wasn't then Python 1 would've been more like
Python 3 and the changes would not have been necessary! :-)