[Python-Dev] Python 4: don't remove anything, don't break backward compatibility

[Steven D'Aprano]

On Mon, Mar 10, 2014 at 02:55:26PM +0100, Victor Stinner wrote:
[...]
> So can we please try to stop scheduling another major Python version
> breaking almost all modules and all applications just to be pendantic?
> 
> No, we should not remove any old feature in Python 4. Python 4 should
> be just a minor release following the previous 3.x release.

I often talk about "Python 4000" as the next possible opportunity for 
major backwards incompatible changes, but of course that's not decided 
yet, and given the long term pain of the 2->3 transition, it may be 
quite conservative, with no radical changes. Perhaps I ought to use 
Python 5000 as my target for radical language changes?


> For example, I propose to release the next major Python version (3.5)
> with the version 4.0 but without removing anything. (It's just an
> example, it can wait another release.) 

If Python 4 is a conservative release, I don't see any reason to bump 
the major version number until after Python 3.9. So, assuming no further 
radical changes to the language like 2->3, we'd have five more point 
releases before needing to deal with 4.0.

Perhaps we need a long-term schedule?

3.5: August 2015
3.6: February 2017
3.7: August 2018
3.8: February 2020
3.9: August 2021
4.0: February 2023

give or take a few months.


-- 
Steven