[Python-Dev] defaultdict proposal round three (original) (raw)

Raymond Hettinger python at rcn.com
Tue Feb 21 00:14:13 CET 2006

[Steven Bethard]

* Should defaultfactory be an argument to the constructor? The three answers I see:

- "No." I'm not a big fan of this answer. Since the whole point of creating a defaultdict type is to provide a default, requiring two statements (the constructor call and the defaultfactory assignment) to initialize such a dictionary seems a little inconvenient.

You still have to allow assignments to the default_factory attribute to allow the factory to be changed:

dd.default_factory = SomeFactory

If it's too much effort to do the initial setup in two lines, a classmethod could serve as an alternate constructor (leaving the regular contructor fully interchangeable with dicts):

dd = defaultdict.setup(list, {'k1':'v1', 'k2:v2'})

or when there are no initial values:

dd = defaultdict.setup(list)

Raymond

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