Multirelease effort: Moving to Python 3

[Daniel P. Berrange]

On Fri, Jul 19, 2013 at 08:20:02AM +0200, Marcela Mašláňová wrote:
> On 07/19/2013 05:44 AM, Toshio Kuratomi wrote:
> >
> >On Jul 18, 2013 5:42 PM, "Michael Catanzaro" <mike.catanzaro at gmail.com
> ><mailto:mike.catanzaro at gmail.com>> wrote:
> > >
> > > On Thu, 2013-07-18 at 09:53 -0700, Toshio Kuratomi wrote:
> > > > /usr/bin/python should refer to python2 --
> > > > http://www.python.org/dev/peps/pep-0394/  I'd be -1 to changing this
> > > But when python2 is no longer installed by default, surely you want to
> > > get a python prompt when you type 'python'?
> >
> >Yes, and for a long time, I'm going to want to get a python2 prompt.
> >Which means installing the package for python2, not having python3 start
> >on that case.
> >
> >
> >
> Why do you want to use old version as default? That's very
> conservative approach for Fedora ;-)

This is not just about porting packages that Fedora is shipping. There are
a quadrillion and one random scripts out in the wild with #!/usr/bin/python
in them, that only work with python2. If Fedora makes /usr/bin/python be a
python3 interpretor, we'll break pretty much all of them. I don't think we
want to be doing that for a very long time yet, if ever.

Far better to encourage people to explicitly use /usr/bin/python2 and
/usr/bin/python3 explicitly and discourage any use of plain /usr/bin/python,
but definitely not change the semantics of the latter.

> Upstream plans to support it until 2015 (maybe little longer).
> Fedora needs to be prepared for such step, so it's the right time to
> start working on it.

Given the amount of python2 code out there, I wouldn't be at all surprised
if someone steps up to maintain python2 beyond the date at which its
current maintainer ceases work. Of course such maintainence work would
likely be important bug fixes & security updates only, not feature work.

So while I encourage a Fedora effort to get onto Python3 by default,
well before 2015, I don't think we should assume that Python2 support
is definitely going to stop in 2015.

Daniel
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