[Python-Dev] Proposal: defaultdict

Aahz aahz at pythoncraft.com
Mon Feb 20 21:38:52 CET 2006

On Mon, Feb 20, 2006, Adam Olsen wrote:
> On 2/20/06, Aahz <aahz at pythoncraft.com> wrote:
>> 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.
> Can you say, for the record (since nobody else seems to care), if
> d.getorset(key, func) would work in your use cases?

Because I haven't been reading this thread all that closely, you'll have
to remind me what this means.

>> Those of you arguing something different: do you have a real use case
>> (that you've implemented in real code)?
> (again, for the record) getorset provides the minimum needed
> functionality in a clean and intuitive way.  Why go for a complicated
> solution when you simply don't need it?

Ditto above.
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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