Summing up rows and columns

[Yoriz]

You could transpose the rows into columns and then use sum

from itertools import zip_longest

rows = [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15, 16]]

print(rows)


def transpose_rows(rows):
    return tuple(zip_longest(*rows, fillvalue=0))


columns = transpose_rows(rows)

print(columns)

print(sum(columns[3]))

Output:
[[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15, 16]]
((1, 5, 9, 13), (2, 6, 10, 14), (3, 7, 11, 15), (4, 8, 12, 16))
40