[BangPypers] partial flattening of list
Vikram
kpguy at rediffmail.com
Tue Jul 27 12:45:10 CEST 2010
Hi Anand,vijay, and others,
we have python 2.4.3 at our workplace and defaultdict is not present in the collections module in this python version.
>>> dir(collections)
['__doc__', '__file__', '__name__', 'deque']
>>>
Also, could u suggest some way to tackle the following problem:
Given:
l = [['NM100', 1, 3], ['NM100', 7, 10], ['NM200', 13, 16]]
want something like:
z = [['NM100',[1,2,3,7,8,9,10]],['NM200',[13,14,15,16]]]
On Tue, 27 Jul 2010 15:33:00 +0530 wrote
>On Tue, Jul 27, 2010 at 3:16 PM, Anand Balachandran Pillai <
abpillai at gmail.com> wrote:
>
>
> On Tue, Jul 27, 2010 at 2:29 PM, Shekhar Tiwatne wrote:
>
>> On Tuesday 27 July 2010 12:18 PM, Vikram wrote:
>>
>>> have the following:
>>>
>>>
>>>
>>>> x
>>>>>>
>>>>>>
>>>>> [['NM100', 1, 2], ['NM100', 3, 4], ['NM200', 5, 6]]
>>>
>>>
>>>> for i in x:
>>>>>>
>>>>>>
>>>>> ... print i
>>> ...
>>> ['NM100', 1, 2]
>>> ['NM100', 3, 4]
>>> ['NM200', 5, 6]
>>>
>>> ------
>>> how does one obtain list z such that
>>>
>>> z = [['NM100',1,2,3,4],['NM200',5,6]]
>>>
>>
> This problem begs for the use of collections.defaultdict class.
>
> All the other solutions are ok, but defaultdict is meant to solve
> problems like this.
>
> Here is the solution.
>
> >>> import collections
> >>> l=[['NM100', 1, 2], ['NM100', 3, 4], ['NM200', 5, 6]]
> >>> l2=[[x[0], x[1:]] for x in l]
> >>> d = collections.defaultdict(list)
> >>> for k, v in l2: d[k].extend(v)
> >>> [[k, v] for k,v in d.iteritems()]
> [['NM100', [1, 2, 3, 4]], ['NM200', [5, 6]]]
>
> What you want are the elements of the final list.
>
I didn't notice you want
z = [['NM100',1,2,3,4],['NM200',5,6]]
rather than,
z= [['NM100', [1, 2, 3, 4]], ['NM200', [5, 6]]]
So replace last line with,
>>> [[k] + v for k,v in d.iteritems()]
[['NM100', 1, 2, 3, 4], ['NM200', 5, 6]]
> --Anand
>
>
>
>
--
--Anand
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