[Python-Dev] Instance variable access and descriptors

[Steven Bethard]

> On 6/10/07, Steven Bethard <steven.bethard at gmail.com> wrote:
> > On 6/9/07, Eyal Lotem <eyal.lotem at gmail.com> wrote:
> > > I believe that this should be changed, so that Python first looks for
> > > the attribute in the instance's dict and only then through the dict's
> > > mro.
> >
> > Are you suggesting that the following code should print "43" instead of "42"?
> > ::
> >
> >     >>> class C(object):
> >     ...     x = property(lambda self: self._x)
> >     ...     def __init__(self):
> >     ...         self._x = 42
> >     ...
> >     >>> c = C()
> >     >>> c.__dict__['x'] = 43
> >     >>> c.x
> >     42

On 6/9/07, Eyal Lotem <eyal.lotem at gmail.com> wrote:
> Yes, I do suggest that.
> But its important to notice that this is not a suggestion in order to
> improve Python, but one that makes it possible to get reasonable
> performance out of CPython. As such, I don't believe it should be done
> in Py3K.
>
> Firstly, like everything that breaks backwards compatibility, it is
> possible to have a transitional version that spits warnings for all
> problems (detect name clashes between properties and instance dict).

Sure, but then you're talking about really introducing this in Python
2.7, with 2.6 as a transitional version. So take a minute to look at
the release timelines:

http://www.python.org/dev/peps/pep-0361/
The initial 2.6 target is for April 2008.

http://www.python.org/dev/peps/pep-3000/
I hope to have a first alpha release (3.0a1) out in the first half of
2007; it should take no more than a year from then before the first
proper release, named Python 3.0

So I'm expecting Python 3.0 to come out *before* 2.7. Thus if you're
proposing a backwards-incompatible change that would have to wait
until 2.7 anyway, why not propose it for 3.0 where
backwards-incompatible changes are more acceptable?

STeVe
-- 
I'm not *in*-sane. Indeed, I am so far *out* of sane that you appear a
tiny blip on the distant coast of sanity.
        --- Bucky Katt, Get Fuzzy