Sum of multiple list of lists index wise

Question

Consider I have a list of lists as:

[[5, 10, 30, 24, 100], [1, 9, 25, 49, 81]]
[[15, 10, 10, 16, 70], [10, 1, 25, 11, 19]]
[[34, 20, 10, 10, 30], [9, 20, 25, 30, 80]]

Now I want the sum of all indexes of first list's index wise and then the 2nd list 5+15+34=54 10+10+20=40 and so on as:

[54,40,50, 50,200], [20,30,75,90,180]

I tried:

for res in results:     
    print [sum(j) for j in zip(*res)] 

Here results is the list of lists. But it gives sum of each list item as:

[6,19,55,73,181]
[25,11,35,27,89]
[43,40,35,40,110]

Answer 1

You are almost correct, you need to unpack results and zip it as well.

>>> data = [[[5, 10, 30, 24, 100], [1, 9, 25, 49, 81]],
...         [[15, 10, 10, 16, 70], [10, 1, 25, 11, 19]],
...         [[34, 20, 10, 10, 30], [9, 20, 25, 30, 80]]]
>>> for res in zip(*data):
...     print [sum(j) for j in zip(*res)] 
... 
[54, 40, 50, 50, 200]
[20, 30, 75, 90, 180]

You can simply write this with list comprehension as

>>> [[sum(item) for item in zip(*items)] for items in zip(*data)]
[[54, 40, 50, 50, 200], [20, 30, 75, 90, 180]]

Answer 2

This is much easier if you use Numpy:

import numpy as np

data = [[[5, 10, 30, 24, 100], [1, 9, 25, 49, 81]],
       [[15, 10, 10, 16, 70], [10, 1, 25, 11, 19]],
       [[34, 20, 10, 10, 30], [9, 20, 25, 30, 80]]]

a = np.array(data)
print a.sum(axis=0)

Output:

[[ 54,  40,  50,  50, 200],
 [ 20,  30,  75,  90, 180]]

Similarly:

In [5]: a.sum(axis=1)
Out[5]:
array([[  6,  19,  55,  73, 181],
       [ 25,  11,  35,  27,  89],
       [ 43,  40,  35,  40, 110]])

In [6]: a.sum(axis=2)
Out[6]:
array([[169, 165],
       [121,  66],
       [104, 164]])

In [7]: a.sum()
Out[7]: 789

Answer 3

You can also use map(), instead.

a = [[5, 10, 30, 24, 100], [1, 9, 25, 49, 81]]
b = [[15, 10, 10, 16, 70], [10, 1, 25, 11, 19]]
c = [[34, 20, 10, 10, 30], [9, 20, 25, 30, 80]]
results = []
for i in range(0, max(len(a), len(b), len(c))):
    results.append(map(lambda x, y, z: x + y + z, a[i], b[i], c[i]))

for result in results:
    for i in result:
        print(i)

But this is unnecessarily long and @thefourtheye's answer is better.