[BangPypers] partial flattening of list

[Anand Balachandran Pillai]

On Tue, Jul 27, 2010 at 4:15 PM, Vikram <kpguy at rediffmail.com> wrote:

>
> 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']
>

>From collections module documentation.

"Changed in version 2.5: Added
defaultdict<http://docs.python.org/library/collections.html#collections.defaultdict>
."

So it is not present in Python <=2.4.



> >>>
>
> 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]]]
>

Why don't you attempt an approach yourself before asking
for help ? Now that you have already seen some solutions
to the first query, isn't that better ?


>
> 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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>
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-- 
--Anand