In [1]:

    

import numpy as np


    

In [2]:

    

a_1d = np.arange(4)
print(a_1d)


    

    




[0 1 2 3]

In [3]:

    

print(a_1d[[0, 2]])


    

    




[0 2]

In [4]:

    

print(a_1d[[0, 3, 2, 1, 2, -1, -2]])


    

    




[0 3 2 1 2 3 2]

In [5]:

    

print(a_1d[np.array([0, 3, 2, 1, 2, -1, -2])])


    

    




[0 3 2 1 2 3 2]

In [6]:

    

a_2d = np.arange(12).reshape(3, 4)
print(a_2d)


    

    




[[ 0  1  2  3]
 [ 4  5  6  7]
 [ 8  9 10 11]]

In [7]:

    

print(a_2d[[0, 2]])


    

    




[[ 0  1  2  3]
 [ 8  9 10 11]]

In [8]:

    

print(a_2d[:, [0, 2]])


    

    




[[ 0  2]
 [ 4  6]
 [ 8 10]]

In [9]:

    

print(a_2d[[0, 2], [0, 2]])


    

    




[ 0 10]

In [10]:

    

print(a_2d[np.ix_([0, 2], [0, 2])])


    

    




[[ 0  2]
 [ 8 10]]

In [11]:

    

print(a_2d[np.ix_([0, 2, 1, 1, -1, -1], [0, 2, 1, 3])])


    

    




[[ 0  2  1  3]
 [ 8 10  9 11]
 [ 4  6  5  7]
 [ 4  6  5  7]
 [ 8 10  9 11]
 [ 8 10  9 11]]

In [12]:

    

print(a_2d[:, [1]])


    

    




[[1]
 [5]
 [9]]

In [13]:

    

print(a_2d[:, [1]].shape)


    

    




(3, 1)

In [14]:

    

print(a_2d[:, 1])


    

    




[1 5 9]

In [15]:

    

print(a_2d[:, 1].shape)


    

    




(3,)