Merge nested list items based on a repeating value

Question

Although poorly written, this code:

marker_array = [[\'hard\',\'2\',\'soft\'],[\'heavy\',\'2\',\'light\'],[\'rock\',\'2\',\'feather\'],[\'fast\',\'3\'], [\'turtl         


        

Answer 1

Quick stab at it... use itertools.groupby to do the grouping for you, but do it over a generator that converts the 2 element list into a 3 element.

from itertools import groupby
from operator import itemgetter

marker_array = [['hard','2','soft'],['heavy','2','light'],['rock','2','feather'],['fast','3'], ['turtle','4','wet']]  

def my_group(iterable):
    temp = ((el + [''])[:3] for el in marker_array)
    for k, g in groupby(temp, key=itemgetter(1)):
        fst, snd = map(' '.join, zip(*map(itemgetter(0, 2), g)))
        yield filter(None, [fst, k, snd])

print list(my_group(marker_array))