Как суммировать элементы векторов типа float

import numpy as np
A = np.array([[-21.56, -0.03, 1.56], [-0.47, 0.46, 1.32], [0.87, 2.68, -0.74], [-0.67, 9.40, 0.25], [1.74, -0.11, 0.31], [-0,76, 8.30, -0.30], [-0.17, -1.33, -1.07], [0.12, 0.07, 0.85], [0.40, 2.32, -0.14], [-2.43, 4.53, -0.87]])
def print_matrix(A):
    for arr in A:
        for el in arr:
            print(el, end = ' ')
        print()
column17 = [];
column18 = [];
column19 = [];
for row in A:
    column17.append(row[0])
    column18.append(row[1])
    column19.append(row[2])
print('2017 год ',column17)
print('2018 год ',column18)
print('2019 год ',column19)

import numpy as np
A = np.array([[-21.56, -0.03, 1.56], [-0.47, 0.46, 1.32], [0.87, 2.68, -0.74], [-0.67, 9.40, 0.25], [1.74, -0.11, 0.31], [-0.76, 8.30, -0.30], [-0.1, -1.33, -1.07], [0.12, 0.07, 0.85], [0.40, 2.32, -0.14]])
column17=A[:,0]
column18=A[:,1]
column19=A[:,2]
print ((column17+column18+column19)/3) # первый вариант
print(np.mean(A, axis=1)) # второй вариант

SR = []
for i in range(len(column17)):
    SR.append((column17[i]+column18[i]+column19[i])/3)
print(SR)

(column17+column18+column19)/3