how to find the sum of list indexes which are given in the sublists of another list in python

Question

i have given a list

myLIST=[34 , 54 , 65 , 76 , 88 , 23 , 56 , 76 , 43]

and a list with the index numbers of myLIST in sublist (assume myLIST starts from index 1)

indexLIST=[{1,2,3} , {4,5,7} , {6,8,9}]

my task is to add the indexes of myLIST according to the sublists of indexLIST

[{34+54+65} , {76,88,23} , {56,76,43}]

res=[153 ,187 , 175]

Note: the sublists of indexLIST are python sets

Answer 1

So first of all there is either a mistake in your indexLIST (set 2 should be {4, 5, 6} and set 3 {7, 8, 9}) or your res (which with the given indexLIST is [153, 220, 142]) otherwise you can just do something like this:

res: list[int] = list()
for set in indexLIST:
    tmp = 0
    for idx in set:
        tmp += myLIST[idx - 1]
    res.append(tmp)

Answer 2

My approach would be to iterate over the sets of indices in index_list and then map these sets to the values of my_list. With sum() I then can compute the sum of each list of values:

my_list=[34 , 54 , 65 , 76 , 88 , 23 , 56 , 76 , 43]
index_list=[{1,2,3} , {4,5,7} , {6,8,9}]

result = [sum(map(lambda x: my_list[x-1], d)) for d in index_list]

print(result)

Output:

[153, 220, 142]

Answer 3

myLIST=[34 , 54 , 65 , 76 , 88 , 23 , 56 , 76 , 43]
indexLIST=[{1,2,3} , {4,5,6} , {7,8,9}]

from pprint import pprint
pprint([sum([myLIST[j-1] for j in i])for i in indexLIST])

Result:

[153, 220, 142]

P.S.

This type of indexing which you're trying to achive could be very fragile, e.g. what if the index, which you're giving doesn't exist in your list ->IndexError ...?