None shown in output

[Xander Solis]

Hello Python list,

Noob here with a newbie question. I'm reading and working on the exercise
of the book, Learn Python the Hard way 2.0. When I use this code, I get
"None" on the output. My question is why does this happen?

def get_numbers(first_num, second_num, operator):

    if operator == 'add':
        print first_num + second_num
    elif operator == 'minus':
        print first_num - second_num
    elif operator == 'divide':
        print first_num / second_num
    elif operator == 'multiply':
        print first_num * second_num

print "%r" % (get_numbers(1, 2, 'minus'))
print "%r" % (get_numbers(1+3, 2+9, 'add'))
print "%r" % (get_numbers(10, 2, 'divide'))

Output:

C:\code\python>ex19.py
-1
None
15
None
5
None
7.5

--

Thanks in advance for your help.

Regards,

Xander
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