import numpy as np
x = [1,2,3]
y = [5,0,1]

def mae(target_y, predicted_y):
    diff = np.array(target_y) - np.array(predicted_y) #diff = [-4, 2, 2]
    absolute = np.absolute(diff) # absolute = [4, 2, 2]
    summation = sum(absolute) # summation = 8
    return summation / len(x) #2.6666666666666665

mae(x,y)