Merging repeated items in a list into a python dictionary

Question

I have a list that looks like the one bellow, with the same item of a pair repeated some times.

l = ([\'aaron distilled \', \'alcohol\', \'5\'], 
[\'aaron di         


        

Answer 1

Use a collections.defaultdict() object for ease:

from collections import defaultdict

result = defaultdict(list)

for key, *values in data:
    result[key].extend(values)

Your first attempty will overwrite keys; a dict comprehension would not merge the values. The second attempt seems to treat the lists in the data list as dictonaries, so that wouldn't work at all.

Demo:

>>> from collections import defaultdict
>>> data = (['aaron distilled ', 'alcohol', '5'], 
... ['aaron distilled ', 'gin', '2'], 
... ['aaron distilled ', 'beer', '6'], 
... ['aaron distilled ', 'vodka', '9'], 
... ['aaron evicted ', 'owner', '1'], 
... ['aaron evicted ', 'bum', '1'], 
... ['aaron evicted ', 'deadbeat', '1'])
>>> result = defaultdict(list)
>>> for key, *values in data:
...    result[key].extend(values)
... 
>>> result
defaultdict(<class 'list'>, {'aaron distilled ': ['alcohol', '5', 'gin', '2', 'beer', '6', 'vodka', '9'], 'aaron evicted ': ['owner', '1', 'bum', '1', 'deadbeat', '1']})

Answer 2

If the items in L are sorted by the first element you can use groupby

>>> L = (['aaron distilled ', 'alcohol', '5'], 
... ['aaron distilled ', 'gin', '2'], 
... ['aaron distilled ', 'beer', '6'], 
... ['aaron distilled ', 'vodka', '9'], 
... ['aaron evicted ', 'owner', '1'], 
... ['aaron evicted ', 'bum', '1'], 
... ['aaron evicted ', 'deadbeat', '1'])
>>> from operator import itemgetter
>>> from itertools import groupby
>>> {k: [j for a,b,c in g for j in b,c] for k, g in groupby(L, itemgetter(0))}
{'aaron evicted ': ['owner', '1', 'bum', '1', 'deadbeat', '1'], 'aaron distilled ': ['alcohol', '5', 'gin', '2', 'beer', '6', 'vodka', '9']}