#!/usr/bin/env python3
import numpy as np

x = np.array([0, 0, 1, 1, 2, 2])
y = np.array([8, 7, 6, 5, 3, 2])
z = np.array([[0, 6],
              [1, 7],
              [2, 8],
              [3, 9]])

print("\nx[:3]    ", x[:3])                # first 3 elements

print("\ny[] %    ", y[int(0.8*len(y)):])  # last 20%

print("\ny[::2]   ", y[::2])               # every second entry

print("\nx!=0     ", x!=0)                 # boolean array

print("\ny[x!=0]  ", y[x!=0])              # filtering

print("\n****************************")

print(z)

print("\nz[:,0]   ", z[:,0])               # only for np arrays

print("\nz[:,1]   ", z[:,1])