random.randint(a, b): [a, b], return ONE random number of between a and b, both a and b are included when acuqiring the number;
random.randint(a, b, size = tuple): [a, b), return random number(s) of between a and b, a included and b is not when acuqiring the number(s), size is 1 by default
e.g.
In [36]: random.randint(1,10) Out[36]: 8 ------------------------------------ In [37]: np.random.randint(10,20) Out[37]: 11 In [38]: np.random.randint(10,20,2) Out[38]: array([19, 15])
