Switching to Python 3

[Toshio Kuratomi]

On Sat, Aug 04, 2012 at 03:50:56AM -0400, Bohuslav Kabrda wrote:
> ----- Original Message -----
> > On Fri, Aug 03, 2012 at 04:42:02AM -0400, Bohuslav Kabrda wrote:
> > > ----- Original Message -----
> > > > On Fri, Aug 3, 2012 at 8:57 AM, Bohuslav Kabrda
> > > > <bkabrda at redhat.com>
> > > > wrote:
> > > > > Hi,
> > > > > I'd like to start a discussion about the release where we
> > > > > should
> > > > > switch to Python 3. As I have learned recently, Ubuntu 12.10
> > > > > will
> > > > > have Python 3 as default [1], which makes me a sad panda :(
> > > > > We always take pride in being close to upstream and having the
> > > > > bleeding edge. Python 3 is stable and more and more libraries
> > > > > support it. So I'd like to propose an idea to switch to Python
> > > > > 3
> > > > > for Fedora 19.
> > > > 
> > > > In which a way do you want to switch to python3?
> > > > For me, that means any mention of "python" is synonym to
> > > > "python3",
> > > > which leads to the question, what is inside a python-foo package?
> > > > The module foo, built for python3?
> > > > 
> > > 
> > > As you say, switching means /usr/bin/python -> /usr/bin/python3.
> > > And yes, that is a very valid point about the naming, I think.
> > > 
> > Porting, taking those ports upstream, and even *tiny shudder*
> > carrying those
> > python3 patches locally for a loooong time, I could support.
> > 
> > Switching /usr/bin/python to point to /usr/bin/python3 I'd be very
> > much
> > against (at least for several years):
> >   http://www.python.org/dev/peps/pep-0394/
> > 
> > has a section that says it may someday be updated to recommend
> > changing
> > a /usr/bin/python symlink to point at python3.  I would wait to make
> > the
> > link change until that PEP is updated (or many other unix
> > distributions are
> > also ready to make the switch).  Switching the link is a largely
> > symbolic
> > gesture that creates more work for package maintainers, more work for
> > end
> > users, and more work for developers (who all have to find uses of
> > /usr/bin/python and change them to /usr/bin/python2).
> > 
> 
> Well, my opinion is different on this. The PEP says that bleeding edge distributions may have python3 as a default. And I like to think of Fedora as bleeding edge.
> 
The only distribution that has switched is arch.  When they did there was
a big uproar about how arch was doing something wrong which eventually
resulted in that PEP.

/usr/bin/python is a program that end users depend on being a certain thing
-- it shouldn't be used to set policy.  That would be like us deciding we
wanted to switch the default shell from /bin/bash to /bin/zsh and to
implement that policy we were going to symlink /bin/bash to /bin/zsh.  Users
wanting /bin/bash would need to update their scripts, tools, and practices
to reference /bin/gnu-bash.

-Toshio
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