Sum combination of lists by element

Question

I have a nested list, which can be of varying length (each sublist will always contain the same number of elements as the others):

list1=[[4.1,2.9,1.2,4.5,7.9,1.2],[0.7,1.1,2.0,0.4,1.8,2.2],[5.1,4.1,6.5,7.1,2.3,3.6]]

I can find every possible combination of sublists of length n using itertools:

n=2
itertools.combinations(list1,n)
[([4.1, 2.9, 1.2, 4.5, 7.9, 1.2], [0.7, 1.1, 2.0, 0.4, 1.8, 2.2]), 
([4.1, 2.9, 1.2, 4.5, 7.9, 1.2], [5.1, 4.1, 6.5, 7.1, 2.3, 3.6]), 
([0.7, 1.1, 2.0, 0.4, 1.8, 2.2], [5.1, 4.1, 6.5, 7.1, 2.3, 3.6])]

I would like to sum all lists in each tuple by index. In this example, I would end up with:

[([4.8, 4.0, 3.2, 4.9, 9.7, 3.4],
[9.2, 7.0, 7.7, 6.8, 10.2, 4.8],
[5.8, 5.2, 8.5, 7.5, 4.1, 5.8])]

I have tried:

[sum(x) for x in itertools.combinations(list1,n)]
[sum(x) for x in zip(*itertools.combinations(list1,n))]

Each run into errors.

Djaouad · Accepted Answer · 2019-09-05 11:43:43Z

2

You can use zip for this:

>>> [tuple(map(sum, zip(*x))) for x in itertools.combinations(list1, n)]
[(4.8, 4.0, 3.2, 4.9, 9.700000000000001, 3.4000000000000004),
 (9.2, 7.0, 7.7, 11.6, 10.2, 4.8),
 (5.8, 5.199999999999999, 8.5, 7.5, 4.1, 5.800000000000001)]

edited Sep 5, 2019 at 11:43

answered Sep 5, 2019 at 11:18

Djaouad

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Arkistarvh Kltzuonstev · Accepted Answer · 2019-09-05 11:22:14Z

1

Try this :

>>> list1=[[4.1,2.9,1.2,4.5,7.9,1.2],[0.7,1.1,2.0,0.4,1.8,2.2],[5.1,4.1,6.5,7.1,2.3,3.6]]
>>> from itertools import combinations as c
>>> list(list(map(sum, zip(*k))) for k in c(list1, 2))
[[4.8, 4.0, 3.2, 4.9, 9.700000000000001, 3.4000000000000004], [9.2, 7.0, 7.7, 11.6, 10.2, 4.8], [5.8, 5.199999999999999, 8.5, 7.5, 4.1, 5.800000000000001]]

answered Sep 5, 2019 at 11:22

Arkistarvh Kltzuonstev

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