how to cut a python list code example

Example 1: python slice an array

a[start:stop]  # items start through stop-1
a[start:]      # items start through the rest of the array
a[:stop]       # items from the beginning through stop-1
a[:]           # a copy of the whole array
Example:
>>> a = [1, 2, 3, 4, 5, 6, 7, 8]
>>> 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]])