如何用常量替换ndarray中每一行的最后一个元素(或任何元素)？

import numpy as np

arr = np.array([[1, 2, 3],
                [4, 5, 6],
                [7, 8, 9]])

constant = 10
arr[:, -1] = constant

constant = 20
arr[:, 1] = constant

import numpy as np

arr = np.array([[1, 2, 3],
                [4, 5, 6],
                [7, 8, 9]])

constant = 10
arr[:, -1] = constant

print(arr)

array([[ 1,  2, 10],
       [ 4,  5, 10],
       [ 7,  8, 10]])