[python-committers] Python 4.0 or Python 3.10?

[Paul Moore]

On Tue, 25 Sep 2018 at 20:32, Antoine Pitrou <antoine at python.org> wrote:
>
>
> Le 25/09/2018 à 21:30, Yury Selivanov a écrit :
> > What's the current plan for what version of Python we release after 3.9?
> >
> > The reason I'm asking this is because I frequently need to refer to
> > *that version* of Python in the documentation, especially when I'm
> > deprecating APIs or behavior.  Right now I'm saying "Python 4.0"
> > implying that 4.0 will be released right after 3.9.
> >
> > I've heard multiple opinions on this subject. One of them is that we
> > should release 4.0 when we have a major new change, like removal of
> > the GIL or introduction of a JIT compiler.  On the other hand, we have
> > no estimate when we have such a change. We also don't want Python 4.0
> > to be backwards incompatible with Python 3.0 (at least not at the
> > scale of 2 vs 3).  So to me, it seems logical that we simply release
> > Python 4.0 after Python 3.9.  After all, after 3.9 Python will be
> > drastically different from 3.0 and from 2.7.  It sounds better. :)
>
> Many people have bad memories of the Py2->3 transition, so I think we
> should avoid triggering their sensitivities by announcing a Py4 if
> there's nothing, in terms of changes, to justify the jump.
>
> So my preference would be on 3.10.

I agree. 3.10 seems like the best choice. Even though we don't expect
4.0 to be a major breaking change like 3.0, people do assume something
like semantic versioning, and therefore expect 3.9 -> 4.0 to be a
"bigger" change than 3.9 -> 3.10.

One thing that *will* need work is places that assume single-digit
version components (for example the wheel spec uses pyXY to mark
compatibility with Python X.Y - that will need tweaking to allow for
3.10). IMO, we should make it clear sooner rather than later that
version numbering will be going 3.8, 3.9, 3.10, 3.11, ... to give
people a chance to prepare. Otherwise we might inadvertently have
another major compatibility issue right after 3.9 :-( The uncertainty
simply lets people assume whatever's least disruptive for them, and
not be ready.

Paul