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

Michael Foord fuzzyman at voidspace.org.uk
Tue Jan 12 23:02:34 CET 2010

On 12/01/2010 21:53, "Martin v. Löwis" wrote:
>>> 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.

I agree with Martin that the *perception* is that to use Python 2.6 to 
help you port to Python 3 you have to be willing to drop support for 
earlier versions of Python.

>>> 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).
Well, the IronPython community has almost completely moved over to 
IronPython 2.6. :-)

We tend to ship our Python runtime with our applications though. As it 
happens I'm now working with CPython on the server (Python 2.5) and 
IronPython in the browser where we are using 2.6. The new property 
feature is nice, as is having with without a __future__ import.

All the best,



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