Thre is a way to do it, even with immutable objects, it is a little bit
heavier :
>>> x = {}
>>> x.setdefault(42,'buckle')
'buckle'
>>> x[42] += '3'
>>> x
{42: 'buckle3'}
Boris Boutillier,
- ARTERIS -
Artwork Interconnecting System
6, Parc Ariane
78284 Guyancourt (FRANCE)
On Thu, 2003-04-03 at 05:04, Greg Ewing wrote:
> Andrew Koenig <ark@research.att.com>:
>
> > So the behavior of
> >
> > foo = d.setdefault(r,'')
> > foo += "test %d\n" % t
> >
> > depends on what type foo has, and the OP didn't say.
>
> I assumed that the code snippet was from his actual application, in
> which case he *did* want it to work on strings, in which case, even if
> he had the feature he wanted, it wouldn't have helped him.
>
> I think the fact that this would only work when the value was mutable
> is a good reason to disallow it. Too big a source of surprises,
> otherwise.
>
> Being forced to find another way to update the value in this case is a
> feature, because the absence of such a way when the value is immutable
> makes it clear that there's no way to do what you're trying to do!
>
> Greg Ewing, Computer Science Dept, +--------------------------------------+
> University of Canterbury, | A citizen of NewZealandCorp, a |
> Christchurch, New Zealand | wholly-owned subsidiary of USA Inc. |
> greg@cosc.canterbury.ac.nz +--------------------------------------+
>
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