On Fri, Jul 2, 2010 at 2:20 AM, Thomas Jollans <tho...@jollans.com> wrote: > On 07/02/2010 06:11 AM, Steven D'Aprano wrote: >> I would like to better understand some of the design choices made in >> collections.defaultdict. <snip> >> Second, why is the factory function not called with key? There are three >> obvious kinds of "default values" a dict might want, in order of more-to- >> less general: >> >> (1) The default value depends on the key in some way: return factory(key) > > I agree, this is a strange choice. However, nothing's stopping you from > being a bit verbose about what you want and just doing it: > > class mydict(defaultdict): > def __missing__(self, key): > # ... > > the __missing__ method is really the more useful bit the defaultdict > class adds, by the looks of it.
Nitpick: You only need to subclass dict, not defaultdict, to use __missing__(). See the part of the docs Raymond Hettinger quoted. Cheers, Chris -- http://mail.python.org/mailman/listinfo/python-list
