How can I sum a column of a list?

Question

I have a Python array, like so:

[[1,2,3],
 [1,2,3]]

I can add the row by doing sum(array[i]), how can I sum a column, using a

Answer 1

Using a for loop (in a generator expression):

data = [[1,2,3],
        [1,2,3]]

column = 1
print(sum(row[column] for row in data))  # -> 4

Answer 2

You can use numpy:

import numpy as np
a = np.array([[1,2,3],[1,2,3]])
a.sum(0)