list comprehension (searching for onliners)

Gerardo Herzig gherzig at fmed.uba.ar
Fri Oct 20 16:47:03 CEST 2006


You are the man, you are the man!! Yes, i need those dicts in order to 
assign them to a nested <TMPL_LOOP> for the htmltmpl templating engine. 
Thats why i cant use the solution provided by Max, and thanks to Jon too!!
Thanks a lot dudes, i hope someday ill turn myself into some of you guys 
who can actually answer questions ;)

Gerardo

>> result = [{'service_id' : 1, 'value': 10},
>>                 {'service_id': 2, 'value': 5},
>>                 {'service_id': 1, 'value': 15},
>>                 {'service_id': 2, 'value': 15},
>>              ]
>>
>> and so on...what i need to do is some list comprehension that returns 
>> me something like
>>
>> result = [
>>                 {
>>                     'service_id' : 1, 'values': [ {'value': 10}, 
>> {'value': 15}]
>>                  },
>>                 {
>>               'service_id' : 2, 'values': [ {'value': 5}, {'value': 15}]
>>                 }
>>               
>> My problem now is i cant avoid have "repeteated" entries, lets say, 
>> in this particular case, 2 entries for "service_id = 1", and other 2 
>> for "service_id =2".
>
>
> Okay...while I'm not sure the opacity of a one-liner is actually 
> productive, it *can* be done.  Whether it should, I leave that to your 
> discernment. :)
>
> >>> [{'service_id': i, 'values':[{'value':d2['value']} for d2 in 
> result if d2['service_id'] == i ]} for i in set(d['service_id'] for d 
> in result)]
>
> [{'service_id': 1, 'values': [{'value': 10}, {'value': 15}]}, 
> {'service_id': 2, 'values': [{'value': 5}, {'value': 15}]}]
>
>
> There's no claiming it's efficient, as it looks like there may be some 
> O(N^2) logic going on under the hood (or possibly O(N*M) where N is 
> the size of the result-set and M is the count of unique service_id 
> values), as it's iterating over the result-set in two 
> dimensions...once to create the set of top-level indices, and once for 
> each result.
>
> If you didn't have to have all those dictionaries around, it might 
> come out more cleanly to just have some result-set that came out to be
>
>     {1: [10,15], 2: [5,15]}
>
> Just a few thoughts...
>
> -tkc
>
>
>
>




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