data standardization

import random
import numpy as np

l, num, gen_min_, gen_max_ = [], 100, 1, 200

l = [random.randint(gen_min_, gen_max_) for i in range(0, num, 1)]
l_std, l_average = np.std(l), np.average(l)
ll = [(i - l_average) / l_std for i in l]
sum_ll = sum(ll)

　　不等于1