[Python-Dev] [RELEASED] Python 2.7 alpha 2

"Martin v. Löwis" martin at v.loewis.de
Tue Jan 12 22:53:01 CET 2010

>> a) telling people that they have to move to 2.6 first actually
>>   hurts migration, instead of helping, because it implies to them
>>   that they have to drop old versions (e.g. 2.3.) - just because
>>   they had *always* dropped old versions before supporting new ones.
> Is it just an implication, or is it reality?

That's only the implication. However, this was precisely the dialogue
when talking to Django. If you start with "start supporting 2.6", the
immediate response, without listening further, was, "ok, wait until we
drop 2.3, which will be in Spring 2009" (it has happened by now, IIUC).

Then explain it to the individual you are talking to, wait for the next
developer of the project step along, and see how he brings up the
very same line of thinking (supporting new versions == dropping support
for old versions).

I think only part of that comes from the maintenance burden. The other
part is that they *want* to drop support for old versions, so that they
can eventually start using new features (e.g. generator expressions).
So they welcome the requirement to support new versions as an excuse
to drop old ones ("it is obvious that you have to drop 2.3 to support
3.2"). However, their users then won't let them drop old versions.

>> b) IMO, people also don't gain much by first migrating to 2.6.
>>   In principle, it gives them the opportunity to get py3k warnings.
>>   However, I haven't heard a single positive report where these
>>   warnings have actually helped people in porting. Yours is the
>>   first report saying that you followed the official guideline,
>>   but you didn't state whether doing so actually helped (or whether
>>   you just ported to 2.6 because the guideline told you to).
> Python 2.6 has other useful features, which I want to take advantage of

I think you are a minority with that, being able to actually use the 2.6
features already. Many projects can't, as they have to support at least
2.4 still (so the with statement is right out).

>> Inherently, 2.8 can't improve on that.
> I'm not so sure.  Yes, as a package maintainer there are older versions to
> think about, but time moves on for everyone (hopefully :).  By the time 2.8 is
> released, what will be the minimum version of Python provided by most OS
> vendors (where the majority of Python users probably get their 'python')?

"Current" Linux distributions will have 2.6 then. "Old" installations
will have 2.4.

> I
> guess some people will have to support everything from Python 2.3 to 2.8 but
> you're talking supporting something like a spread of 7 years of Python
> versions.  What other platform do you support for 7 years?

I think 2.3 will really be gone by the time 2.8 might get released. Even
with 2.7, you'd end up with a span of seven years, though.

Python had been supporting Windows 95 for more than 7 years (I think
rather 9 or 10), likewise Windows 3.1 before that. Python 2.7 will
likely still support Windows 2000, which then will be ten years old.

Solaris support will probably go back to Solaris 2.6, which will be
13 years old when Python 2.7 gets released.

It's only the Linux (and OS X) releases that move so quickly.


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