list(delta([1, 2, 4, 7, 11])) == [1, 2, 3, 4] because 2-1 == 1, 4-2 == 2, 7-4 == 3, 11-7 == 4 code example

Example: how to import numpy array in python

>>> import numpy as np
>>> a = np.array([0, 1, 2, 3])
>>> a
array([0, 1, 2, 3])