for each data point in the data set numpy array code example

Example 1: how to get the first few lines of an ndarray 3d

>>> import numpy as np
>>> v = np.array(np.arange(24)).reshape(2,3,4)
>>> v
array([[[ 0,  1,  2,  3],
        [ 4,  5,  6,  7],
        [ 8,  9, 10, 11]],

       [[12, 13, 14, 15],
        [16, 17, 18, 19],
        [20, 21, 22, 23]]])
>>> v[:, 1, 3]
array([ 7, 19])

Example 2: how to get the first few lines of an ndarray

In [11]: a[:,:2]
Out[11]: 
array([[-0.57098887, -0.4274751 ],
       [-0.22279713, -0.51723555],
       [ 0.67492385, -0.69294472],
       [ 0.41086611,  0.26374238]])