unintuitive dict timings

[Dave Benjamin]

In article <3f89e8bf$1_1 at dns.sd54.bc.ca>, Bob van der Poel wrote:
> 
> Alex Martelli wrote:
> 
>> 
>> def sede(key, val):
>>     d.setdefault(key, []).append(val)
>> 
>> appears to be very marginally fastest, but again it's a close call:
> 
> Ahhh, an example of setdefault(). I looked at this in the docs but it 
> really didn't make much sense.... I'll give this a try just to see what 
> difference it makes.

Another solution would be to subclass dict to make a dictionary that
automatically creates lists as needed. For example:

class dict_of_lists(dict):
    def __getitem__(self, key):
        try:
            return dict.__getitem__(self, key)
        except KeyError:
            self[key] = []
            return self[key]

dol = dict_of_lists()
dol['a'].append(1)
dol['b'].append(2)
dol['c'].append(3)
dol['c'].append(4)
dol['c'].append(5)
print dol

Output: {'a': [1], 'c': [3, 4, 5], 'b': [2]}

-- 
.:[ dave benjamin (ramenboy) -:- www.ramenfest.com -:- www.3dex.com ]:.
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