5.4. Indexing New Axis

5.4.1. Recap

>>> import numpy as np
>>>
>>>
>>> a = np.array([[1, 2, 3],
...               [4, 5, 6],
...               [7, 8, 9]])
>>>
>>> a[:, 1]
array([2, 5, 8])
>>>
>>> a[:, 0:2]
array([[1, 2],
       [4, 5],
       [7, 8]])

5.4.2. With Indexes

>>> import numpy as np
>>>
>>>
>>> a = np.array([[1, 2, 3],
...               [4, 5, 6],
...               [7, 8, 9]])
>>>
>>> a[:, 1]
array([2, 5, 8])
>>>
>>> a[np.newaxis, :, 1]
array([[2, 5, 8]])
>>>
>>> a[:, np.newaxis, 1]
array([[2],
       [5],
       [8]])
>>>
>>> a[:, 1, np.newaxis]
array([[2],
       [5],
       [8]])

5.4.3. With Slices

>>> import numpy as np
>>>
>>>
>>> a = np.array([[1, 2, 3],
...               [4, 5, 6],
...               [7, 8, 9]])
>>>
>>> a[:, 0:2]
array([[1, 2],
       [4, 5],
       [7, 8]])
>>>
>>> a[np.newaxis, :, 0:2]
array([[[1, 2],
        [4, 5],
        [7, 8]]])
>>>
>>> a[:, np.newaxis, 0:2]
array([[[1, 2]],

       [[4, 5]],

       [[7, 8]]])
>>>
>>> a[:, 0:2, np.newaxis]
array([[[1],
        [2]],

       [[4],
        [5]],

       [[7],
        [8]]])