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

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e.g.

In [36]: random.randint(1,10)
Out[36]: 8
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In [37]: np.random.randint(10,20)
Out[37]: 11

In [38]: np.random.randint(10,20,2)
Out[38]: array([19, 15])