Static variable vs Class variable

[Paul Melis]

On Oct 17, 3:20 pm, Marc 'BlackJack' Rintsch <bj_... at gmx.net> wrote:
> On Wed, 17 Oct 2007 05:57:50 -0700, Paul Melis wrote:
> > On Oct 17, 2:39 pm, Duncan Booth <duncan.bo... at invalid.invalid> wrote:
> >> >>> class C(object):
>
> >>         def setx(self, value):
> >>                 if len(value)>2:
> >>                         raise ValueError
> >>                 self._x = value
> >>         def getx(self):
> >>                 return self._x
> >>         x = property(getx, setx)
>
> >> >>> o = C()
> >> >>> o.x = []
> >> >>> o.x += ['a']
> >> >>> o.x += ['b']
> >> >>> o.x += ['c']
>
> >> Traceback (most recent call last):
> >>   File "<pyshell#27>", line 1, in <module>
> >>     o.x += ['c']
> >>   File "<pyshell#22>", line 4, in setx
> >>     raise ValueError
> >> ValueError
>
> >> >>> o.x
> >> ['a', 'b', 'c']
>
> > Now that's really interesting. I added a print "before" and print
> > "after" statement just before and after the self._x = value and these
> > *do not get called* after the exception is raised when the third
> > element is added.
>
> Well, of course not.  Did you really expect that!?  Why?

Because o.x *is* updated, i.e. the net result of self._x = value is
executed.

Paul