merging sublists based on repeated values in another list

Question

I have 2 lists from which I would like to create a dict.

my list1 is:

[1,2,2,3]

my list2 is:

[['A','B'],['J','K'],[L'','M'],['W','X']]

I would like to make a

dict(zip(list1,list2))

However given that list1 has a repeated key I am loosing one key 2 with its values.

So I would like to join the sublists of list2 based on the repeated values in list 1 .

list1 and list2 are indexed in same order.

The desired output would be :

[['A','B'],['J','K','L','M'],['W','X']]

So I can remove dups of list1 and make the

dict(zip(list1_without_dups,list2_merged_sublists))

Sorry I do not include my try but i have been seeking for similar issues unsuccesfully and not sure how to face it.

Austin · Accepted Answer · 2019-08-11 15:46:11Z

4

Use collections.defaultdict:

from collections import defaultdict

lst1 = [1,2,2,3]
lst2 = [['A','B'],['J','K'],['L','M'],['W','X']]

d = defaultdict(list)

for x, y in zip(lst1, lst2):
    d[x].extend(y)

print(d)

which outputs:

defaultdict(<class 'list'>, {1: ['A', 'B'], 2: ['J', 'K', 'L', 'M'], 3: ['W', 'X']})

You can now extract values to get the desired list.

edited Aug 11, 2019 at 15:46

answered Aug 11, 2019 at 15:35

Austin

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Ajax1234 · Accepted Answer · 2019-08-11 15:36:28Z

0

You can use itertools.groupby:

from itertools import groupby as g, chain as c
d =  [1,2,2,3]
new_d = [['A','B'],['J','K'],['L','M'],['W','X']]
r = [list(c(*[j for _, j in b])) for _, b in g(list(zip(d, new_d)), key=lambda x:x[0])]

Output:

[['A', 'B'], ['J', 'K', 'L', 'M'], ['W', 'X']]

answered Aug 11, 2019 at 15:36

Ajax1234

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