I am not able to understand why I am getting the output like this for the second print statement. Could u pls help me out

Question

import re

print(re.sub(r'AB?', '*', 'ABBBCD'))
# OUTPUT - *BBCD

print(re.sub(r'AB??', '*', 'ABBBCD'))
# OUTPUT - *BBBCD

Answer 1

Which Output do you expect then or what should come out?

Answer 2

Felix Alcor I am asking for the reason or explanation as to why I am getting that output.

Answer 3

Seems like Double '??' only take the first char and not the second.
Here some Testing I have done.
https://code.sololearn.com/c7pDd7kOM2I1/?ref=app