[Python-Dev] Proposal: defaultdict (original) (raw)

Fredrik Lundh fredrik at pythonware.com
Fri Feb 17 12:14:27 CET 2006

Guido van Rossum wrote:

A bunch of Googlers were discussing the best way of doing the following (a common idiom when maintaining a dict of lists of values relating to a key, sometimes called a multimap):

if key not in d: d[key] = [] d[key].append(value)

/.../

Feedback?

+1. check it in, already (as collections.defaultdict, perhaps?)

alternatively, you could specialize even further: collections.multimap, which deals with list values only (that shallow copy thing feels a bit questionable, but all alternatives feel slightly overgeneralized...)

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