[Python-Dev] Proposal: defaultdict

Ian Bicking ianb at colorstudy.com
Fri Feb 17 22:03:49 CET 2006

Guido van Rossum wrote:
> d = {}
> d.default_factory = set
> ...
> d[key].add(value)

Another option would be:

   d = {}
   d.default_factory = set

Unlike .setdefault, this would use a factory associated with the 
dictionary, and no default value would get passed in.  Unlike the 
proposal, this would not override __getitem__ (not overriding 
__getitem__ is really the only difference with the proposal).  It would 
be clear reading the code that you were not implicitly asserting they 
"key in d" was true.

"get_default" isn't the best name, but another name isn't jumping out at 
me at the moment.  Of course, it is not a Pythonic argument to say that 
an existing method should be overridden, or functionality made nameless 
simply because we can't think of a name (looking to anonymous functions 
of course ;)

Ian Bicking  /  ianb at colorstudy.com  /  http://blog.ianbicking.org

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