How do I add indefinite number of list together and output a single list?

Question

The inputs will be lists (which is the number of list is indefinite), the function is supposed to iterate through all the index and add each value of the list for same index for all the inputted list mathematically together. The output will be the a list which consist of all the added values

For example: lista = [1,2,3] listb = [2,3,5] listc = [-3,2,1] outputlist = [0,7,9] My function below is only able to add 2 list together, I want no restrictions as to how many list. How do I do that? Thank you very much in advance

def listadd(a,b):
    counter = 0
    list = []
    while counter < len(a):
        list.append(a[counter]+b[counter])
        counter += 1
    return list

Please include more information about expected inputs/outputs. — Jim Stewart, Nov 11 '18 at 15:22
Side note: **never** (even as an example) shadow built-ins, e.g. use `lst`, `L` or `list_` instead of `list` as your argument name. — jpp, Nov 11 '18 at 15:26
Sorry for not being specific in the question, I meant to add each values of the same list index mathematically, not combining the list. — Royston Teo, Nov 11 '18 at 15:34
@jonrsharpe I have seen that example, however I do not know how to add the values of same index mathematically together. — Royston Teo, Nov 11 '18 at 15:36

score 2 · Accepted Answer · answered Nov 11 '18 at 15:25

2

You can use map with zip:

def listadd_new(*lsts):
    return list(map(sum, zip(*lsts)))

assert listadd([1, 2, 3], [4, 5, 6]) == listadd_new([1, 2, 3], [4, 5, 6])

answered Nov 11 '18 at 15:25

jpp

159,742
34
281
339

1

Or with a list comprehension for increased readability: `return [sum(values) for values in zip(*lsts)]` – soundstripe Nov 11 '18 at 15:41
1

https://docs.python.org/3/library/functions.html#zip – soundstripe Nov 11 '18 at 15:44

How do I add indefinite number of list together and output a single list?

1 Answers1