how to read elements of a column in an array do some computation and inset the value to new array in python code example

Example 1: code for dimensions in numpy

import numpy as np

arr = np.array([1, 2, 3, 4])
arr_2D = np.array([[1, 2, 3, 4, 5], [6, 7, 8, 9, 10]])

print(arr.ndim)
print(arr_2D.ndim)

Example 2: 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])