python生成单位阵或对角阵的三种方式小结_python

import numpy as np

np.identity(4)
array([[ 1., 0., 0., 0.],
       [ 0., 1., 0., 0.],
       [ 0., 0., 1., 0.],
       [ 0., 0., 0., 1.]])

np.eye(4)
array([[1., 0., 0., 0.],
       [0., 1., 0., 0.],
       [0., 0., 1., 0.],
       [0., 0., 0., 1.]])

np.diag([1] * 4)
Out[1]: 
array([[1, 0, 0, 0],
       [0, 1, 0, 0],
       [0, 0, 1, 0],
       [0, 0, 0, 1]])
np.diag([2] * 4)
Out[2]: 
array([[2, 0, 0, 0],
       [0, 2, 0, 0],
       [0, 0, 2, 0],
       [0, 0, 0, 2]])

np.eye(N,M=None,k=0,dtype=<class 'float'>,order='C)

    a = np.eye(4)
    print(type(a))
    print(a)
    a = np.mat(a)
    print(type(a))
    print(a)
    a = a.I
    print(type(a))
    print(a)
>>><class 'numpy.ndarray'>
[[1. 0. 0. 0.]
 [0. 1. 0. 0.]
 [0. 0. 1. 0.]
 [0. 0. 0. 1.]]
<class 'numpy.matrix'>
[[1. 0. 0. 0.]
 [0. 1. 0. 0.]
 [0. 0. 1. 0.]
 [0. 0. 0. 1.]]
<class 'numpy.matrix'>
[[1. 0. 0. 0.]
 [0. 1. 0. 0.]
 [0. 0. 1. 0.]
 [0. 0. 0. 1.]]

    a = np.eye(4,k=1)
    print(type(a))
    print(a)
    a = np.mat(a)
    print(type(a))
    print(a)
    a = a.T
    print(type(a))
    print(a)
>>><class 'numpy.ndarray'>
[[0. 1. 0. 0.]
 [0. 0. 1. 0.]
 [0. 0. 0. 1.]
 [0. 0. 0. 0.]]
<class 'numpy.matrix'>
[[0. 1. 0. 0.]
 [0. 0. 1. 0.]
 [0. 0. 0. 1.]
 [0. 0. 0. 0.]]
<class 'numpy.matrix'>
[[0. 0. 0. 0.]
 [1. 0. 0. 0.]
 [0. 1. 0. 0.]
 [0. 0. 1. 0.]]