把向量放到一个list中，用for i in list进行遍历
循环数字时为for i in range(num)

import numpy as np

# 列向量乘行向量
x1 = np.array([[1,2]]).T
x2 = np.array([[1,3]]).T
x = [x1, x2]
res = 0
for i in x:
    res += i * i.T;
print(res)