[Python-Dev] [PEP] += on return of function call result (original) (raw)

Boris Boutillier boris.boutillier@arteris.net
03 Apr 2003 08:09:11 +0200

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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