twp ways to slice in python code example

Example 1: python array slice

>>> a[1:4]
[2, 3, 4]

Example 2: python slice second element of list of lists

import numpy as np

A = np.array([[1,2,3,4,5],[1,2,3,4,5],[1,2,3,4,5]])
A[:,:3]

Out[3]: 
array([[1, 2, 3],
       [1, 2, 3],
       [1, 2, 3]])