[Python-Dev] collections module
Martin v. Loewis
martin at v.loewis.de
Sat Jan 10 17:35:16 EST 2004
Robert Brewer wrote:
> This seems a bit too easy to do "as needed" to warrant a new builtin,
> but that's why we have proposals, I guess:
>
> class DefaultingDict(dict):
>
> def __init__(self, default):
> self.default = default
>
> def __getitem__(self, key):
> return self.get(key, self.default())
It would not necessarily have to be a builtin, but it should be part
of the standard library somewhere. Having to write it anew everytime
you need it is too tedious, so I usually have a try:except: block,
doing the defaulting in the except: part.
There would be also more semantic issues, such as whether has_key
should always return True on a DefaultingDict. Your implementation
is incomplete, too - .pop() should invoke the default function, as
should .get().
Regards,
Martin
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