Covariance Between Two Variables

def covariance(x, y):
    mx = sum(x) / len(x)
    my = sum(y) / len(y)
    total = 0
    for i in range(len(x)):
        total += (x[i] - mx) * (y[i] - my)
    return total

print(covariance([1, 2, 3], [4, 5, 6]))