Sum Parts of Multiple Lists

Question

I'm sure there is a good way to accomplish what i want without looping over lists and creating new objects. Here is what I have

a = [1, 2, 3, 4]
b = [2, 3, 4, 5]

What I am looking to do is take each set of lists and sum each placeholder so that the output is

[3, 5, 7, 9]

Thoughts?

So, is an [element-wise sum](http://stackoverflow.com/questions/18713321/element-wise-addition-of-2-lists-in-python) what you're looking for? — Alex Riley, Apr 29 '15 at 14:12
The `map` method doesn't return a `list` anymore in python3. You would have to call `list(map(...))` to get a list back again. — Bhargav, Apr 29 '15 at 14:15

score 4 · Accepted Answer · answered Apr 29 '15 at 14:13

4

you should use zip function and list comprehension

a = [1, 2, 3, 4]
b = [2, 3, 4, 5]
[sum(t) for t in zip(a,b)]

answered Apr 29 '15 at 14:13

score 2 · Answer 2 · answered Apr 29 '15 at 14:13

2

Use numpy

import numpy as np
a = np.array([1, 2, 3, 4])
b = np.array([2, 3, 4, 5])
a+b
>>> array([3, 5, 7, 9])

answered Apr 29 '15 at 14:13

DilithiumMatrix

2 Answers2