How to sum columns of an array in Python

Question

How do I add up all of the values of a column in a python array? Ideally I want to do this without importing any additional libraries.

input_val = [[1, 2, 3,         


        

Answer 1

Try this code. This will make output_val end up as [3, 6, 9, 12, 15] given your input_val:

input_val = [[1, 2, 3, 4, 5],
             [1, 2, 3, 4, 5],
             [1, 2, 3, 4, 5]]

vals_length = len(input_val[0])
output_val = [0] * vals_length # init empty output array with 0's
for i in range(vals_length): # iterate for each index in the inputs
    for vals in input_val:
        output_val[i] += vals[i] # add to the same index

print(output_val) # [3, 6, 9, 12, 15]