'python: pointwise list sum

Input: two lists (list1, list2) of equal length
Output: one list (result) of the same length, such that:
    result[i] = list1[i] + list2[i]

Is there any concise way to do that? Or is this the best:

# Python 3
assert len(list1) == len(list2)
result = [list1[i] + list2[i] for i in range(len(list1))]

python list

Solution 1:^[1]

IMO the nicest way is

result = [x + y for x, y in zip(list1, list2)]

with Python3 basic zip is not even building an intermediate list (not an issue unless list1 and list2 lists are huge).

Note however that zip will stop at the shortest of the input lists, so your assert is still needed.

Solution 2:^[2]

[a + b for a, b in zip(list1, list2)]

Solution 3:^[3]

There are several ways, e.g. using map, sum and izip (but afaik, zip works the same as izip in Python 3):

>>> from itertools import izip
>>> map(sum, izip(list1, list2))

Solution 4:^[4]

I'd do:

result = [x+x for x,y in zip(list1, list2)]

Solution 5:^[5]

using the + as pointwise sum is the default operation on numpy arrays.
the * operator likewise is the pointwise multiplikation:

import numpy as np
list1 = np.array(list1)
list2 = np.array(list2)
assert list(list1+list2) == list([list1[i] + list2[i] for i in range(len(list1))])
assert list(3*list1) == list([3*list1[i] for i in range(len(list1))])

comparing two list equal with == does not work with np arrays though.

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source
Solution 1	6502
Solution 2	Ignacio Vazquez-Abrams
Solution 3	Felix Kling
Solution 4	vartec
Solution 5	Johann Wiengold

'python: pointwise list sum

Solution 1:[1]

Solution 2:[2]

Solution 3:[3]

Solution 4:[4]

Solution 5:[5]