[python-committers] Deprecation Policy PEP

[R. David Murray]

On Tue, 02 Feb 2016 15:33:58 +0200, Ezio Melotti <ezio.melotti at gmail.com> wrote:
> On Sat, Jan 30, 2016 at 5:36 AM, Guido van Rossum <guido at python.org> wrote:
> > Following the lead of 2.7.10 and 2.7.11 we could continue with 3.10, 3.11, etc.
> >
> 
> I think we should continue with 3.10, 3.11, etc.
> Changing the major version should be done for incompatible changes,
> and just doing it after 3.9 will probably just create confusion for
> both users that will wonder if it's incompatible with Python 3 and for
> things like the executable name.
> Hopefully we won't need to jump to Python 4 for a long time.
> 
> > I also want the 3->4 transition to feel like a non-event for most
> > users. How we'll do that I don't know yet, but I want it to be a lot
> > smoother than 2->3.

I think Guido's point is that we shouldn't *make* incompatible changes,
and that the 4.0 transition should be smooth so that people learn we are
committed to that.  This is potentially analogous to the linux
transition from 2.x to 3.x, despite the fact that it goes against the
rules of semantic versioning.

That said, I don't view removing deprecated things as a incompatible
change, since code that has dealt with the deprecations will run on both
the version before (usually versions plural) and the version after the
removal.  Whether we should do a mass removal in 4.0 (or the first post
2.7 release) is a question, and so far the sense I get of the community
is that there is not even close to a consensus on that.  But it would
give a semantic versioning meaning to the change from 3.x to 4.x,
without actually being all that disruptive.  On the other hand, a mass
removal would be more disruption than removals spaced over several
releases, so FUD might well arise as an issue, as you say.

Regardless though, the name is an issue :)

So, I guess I see the arguments between going 3.9->4.0 vs 3.9->3.10
as fairly balanced and don't have a strong preference.

--David