[Python-Dev] Python-3 transition in Arch Linux

[Thomas Wouters]

On Fri, Nov 5, 2010 at 17:09, Stephen J. Turnbull <stephen at xemacs.org>wrote:

> Thomas Wouters writes:
>
>  > > This is unrealistic.  It would seriously annoy Arch's intended
>  > > audience.  (Eg, recently I've become a lot more favorable to using
>  > > Word instead of OOo because Word doesn't pop up a useless warning
>  > > every time I save a .doc file.)  Practically speaking, it would have
>  > > to be off by default, like Python pending deprecation warnings.
>  >
>  > Wait, what? Warning about impending brokenness is *more annoying* than
> just
>  > plain breaking? How on earth would the warning be "useless"?
>  > Keep in mind that the warning would only show up *if stuff would
> otherwise
>  > not work*.
>
> As I understood it, what you proposed was that in a *Python 2-based*
> distribution thinking about switching to Python 3 as the default
> /usr/bin/python, they should first substitute a bitch'n'run-python2
> script for the python (Python 2) binary, and after that works the bugs
> out, switch to Python 3.
>
> In that scenario, the bitching is useful *exactly* once: the first
> time anybody reports the bug to someone who can do something about it.
> But for some time, *every time* you run your app, it bitches
> uselessly: it would work fine if you just install Python 2 as
> /usr/bin/python, without bitching.  That's not very graceful.  And
> "some time" will often stretch into weeks or months for any given
> user, since few distros will bless a new package with zero testing.
>

No, what I suggested was that *instead of changing /usr/bin/python to Python
3*, it would produce a warning. So, as before, change everything you know
about to python2. Keep everything that is python3 using python3. Change
/usr/bin/python, which *should* now be unused, to something that complains.
Since all the distribution-installed packages were changed, the only
warnings will come from invocations that would otherwise have spectacularly
and possibly quite confusingly blown up. As I said, the warning can provide
clear instructions on updating the software. Heck, the /usr/bin/python
wrapper could be made to be quiet for a day at a time by having the user
press a button.


>  > No, that's not my point at all. The problem isn't that Python 3 is
>  > incompatible with Python 2. The problem is that stuff broke without
>  > (apparently) fair warning.
>
> Warning was given; they weren't listening.
>

Yes, that's what users do. They don't look at the websites or read the
mailinglists, they just care that their stuff keeps working and they don't
want to pay the maintenance cost :) I'm not saying Arch should have done
this, but most Linux distributions do *not* have attentive users. This is
not news. I would rather we stay with an explicit 'python3' for another
decade (as, after all, Perl did with perl5 as well) than that more people
are confronted with the switch to python3 by having their own code break.

-- 
Thomas Wouters <thomas at python.org>

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