如何对 Python 中的 2D 矩阵中的所有列求和？

Question

I used the following code to sum all the rows in a 2D matrix but I want to sum all the columns instead:

row_sum = sum(map(sum,[arr]))

Answer 1

You can try the code below:

import numpy as np
arr: <2D matrix> 
col_sum = np.sum(arr, axis=1, keepdims=True)