[BangPypers] partial flattening of list

[Shekhar Tiwatne]

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]]
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>    
A less readable solution using itertools

#------------
from itertools import *

get_first = lambda x: x[0]
filter_first_and_chain_rest = lambda seq: chain(*(x[1:] for x in seq))

data = [['NM100', 1, 2], ['NM100', 3, 4], ['NM200', 5, 6]]
grouped = groupby(sorted(data), get_first)
print list ([label] + list(filter_first_and_chain_rest(grp)) for label, 
grp in grouped)


~Shekhar