[Python-Dev] dict.addlist() (original) (raw)

Barry Warsaw barry at python.org
Tue Jan 20 09:52:05 EST 2004

On Tue, 2004-01-20 at 09:26, Bob Ippolito wrote:

On Jan 20, 2004, at 9:17 AM, Raymond Hettinger wrote:

> Here is anidea to kick around: > > Evolve and eventually replace dict.setdefault with a more specialized > method that is clearer, cleaner, easier to use, and faster. > > d.addlist(k, v) would work like d.setdefault(k, > []).append(v) -1 There are other reasons to use setdefault. This one is pretty common though, but I think a more generic solution could be implemented. Perhaps: d.setdefault(k, factory=list).append(v) ?

d.setdefault(k, []).append(v)

I'm not sure what any of the other suggestions buy you except avoiding a list instantiation, which doesn't seem like enough to warrant the extra complexity. I use setdefault() quite a bit (big surprise, huh?) and occasionally would like lazy evaluation of the second argument, but it usually doesn't bother me.

-Barry

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