import numpy as np
array_2d = np.array([
   [1, 2, 3, 4],
   [5, 6, 7, 8],
   [9, 10, 11, 12]
])
print(array_2d[1:])
print(array_2d[:, 0])
print(array_2d[1:, 1:-1])
print(array_2d[:-1, ::2]) 
print(array_2d[2, ::-2])

array = np.array([23, 41, 7, 80, 3])
# Retrieving elements at indices 0, 1 and 3
print(array[[0, 1, 3]])
# Retrieving elements at indices 1, -1 and 2 in this order
print(array[[1, -1, 2]])
# IndexError is thrown since index 5 is out of bounds
print(array[[2, 4]])