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

Aahz aahz at pythoncraft.com
Mon Feb 20 16🔞08 CET 2006

On Sun, Feb 19, 2006, Josiah Carlson wrote:

I agree, there is nothing perfect. But at least in all of my use-cases, and the majority of the ones I've seen 'in the wild', my previous post provided an implementation that worked precisely like desired, and precisely like a regular dictionary, except when accessing a non-existant key via: value = dd[key] . contains, etc., all work exactly like they do with a non-defaulting dictionary. Iteration via popitem(), pop(key), items(), iteritems(), iter, etc., all work the way you would expect them.

This is the telling point, IMO. My company makes heavy use of a "default dict" (actually, it's a "default class" because using constants as the lookup keys is mostly what we do and the convenience of foo.bar is compelling over foo['bar']). Anyway, our semantics are as Josiah outlines, and I can't see much use case for the alternatives.

Those of you arguing something different: do you have a real use case (that you've implemented in real code)?

Aahz (aahz at pythoncraft.com) <*> http://www.pythoncraft.com/

"19. A language that doesn't affect the way you think about programming, is not worth knowing." --Alan Perlis

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