003《Python数据分析、挖掘与可视化(第2版)》/6.2.8.py
import numpy as np

x = np.matrix([[1,2,3], [4,5,6], [7,8,0]])
y = np.linalg.inv(x)
print(y)
print(x*y)          # 对角线元素为1,其他元素为0或近似为0
print(y*x)