sum of surrounding elements in a list

Question

I'm writing a code which calculates the sum of the numbers beside it.

For example, list1 = [10, 20, 30, 40, 50], the new list = [30 (10+20), 60 (10+20+30), 90 (20+30+40), 120 (30+40+50), 90 (40+50)]. => final list = [30, 60, 90, 120, 90].

At the moment my idea was of using a for loop but it was totally off.

Does this answer your question? [Rolling or sliding window iterator?](https://stackoverflow.com/questions/6822725/rolling-or-sliding-window-iterator) — Karl Knechtel, Sep 07 '22 at 07:55

score 0 · Answer 1 · answered Mar 07 '16 at 09:17

0

You can do it by creating triplets using zip:

# pad for first and last triplet
lst = [0] + original + [0]
# summarize triplets
sums = [sum(triplet) for triplet in zip(lst, lst[1:], lst[2:])]

Example:

>>> original = [10, 20, 30, 40, 50]
>>> lst = [0] + original + [0]
>>> sums = [sum(triplet) for triplet in zip(lst, lst[1:], lst[2:])]
>>> sums
[30, 60, 90, 120, 90]
>>>

answered Mar 07 '16 at 09:17

Reut Sharabani

30,449
6
70
88

If this answers your question you can accept it as the answer. – Reut Sharabani Mar 07 '16 at 09:30

score 0 · Answer 2 · edited May 23 '17 at 10:28

0

Check out this guy's flatten function What is the fastest way to flatten arbitrarily nested lists in Python?

Take the result of the flattened lists of lists and sum the collection normally with a for loop, or a library that provides a count utility for collections.

edited May 23 '17 at 10:28

Community

1
1

answered Mar 07 '16 at 09:19

hansod1

314
1
4

sum of surrounding elements in a list

2 Answers2