import timeit

print(timeit.timeit("list_1[:][:]", 
      setup="list_1 = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]"))

print(timeit.timeit("list_2[:,]", 
      setup="import numpy as np; list_2 = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]])"))