default behavior

Ethan Furman ethan at
Wed Aug 4 00:15:40 CEST 2010

John Posner wrote:
> On 7/31/2010 1:31 PM, John Posner wrote:
>> Caveat -- there's another description of defaultdict here:
>> ... and it's bogus. This other description claims that __missing__ is a
>> method of defaultdict, not of dict.

__missing__ isn't a method of dict:

--> print dir(dict())
['__class__', '__cmp__', '__contains__', '__delattr__', '__delitem__',
  '__doc__', '__eq__', '__ge__', '__getattribute__', '__getitem__',
  '__gt__', '__hash__', '__init__', '__iter__', '__le__', '__len__',
  '__lt__', '__ne__', '__new__', '__reduce__', '__reduce_ex__',
  '__repr__', '__setattr__', '__setitem__', '__str__', 'clear', 'copy',
  'fromkeys', 'get', 'has_key', 'items', 'iteritems', 'iterkeys',
  'itervalues', 'keys', 'pop', 'popitem', 'setdefault', 'update',

I will agree that the current defaultdict description does not make it 
clear that __missing__ can be defined for *any* subclass of dict, 
although the dict description does go over this... is that the confusion 
you are talking about?  If not, could you explain?


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