Python中数组和矩阵可以转换吗？

from numpy import *

a1 = [[1,2,3],[4,5,6],[7,8,9]]

#数组转换为矩阵

a2 = mat(a1)

print("\n数组a1--->矩阵a2：\n",a2)

#矩阵转换为数组

a3 = mat([1,2])

a4 = a3.A

print("\n矩阵a3--->数组a4：\n",a4)

python -m pip install --upgrade pip

pip install numpy