Why doesent this repeat loop work as intended when the user first triggers the else statement and then answers yes?

Question

def repeat():
    ques = input("Would you like to repeat the program? (yes or no): ").lower()

    if ques == "yes":
        return True

    elif ques == "no":
        exit()

    else:
        repeat()


bool = True
while bool:
    bool = repeat()

Answer 1

Okay so... The first thing you've done wrong is to use recursion to repeat the program: https://en.wikipedia.org/wiki/Recursion.

By default in python, a function returns 'None':

>>> def f():
...     x = 0
... 
>>> print(f())
None

see https://realpython.com/python-return-statement/.

And in a whileloop None is considered as False as it is not True.

So when your function ends here after the execution of repeat :

...
    else:
        repeat()

the function returns None value instead of True, and therefore the while loop ends.

You should instead use :

...
else:
    return repeat()

which will return what repeat() returns (True in case of the following answer "yes").

However I would have not done the program like this.

def repeat():
    r = True
    while r:
       ques = input(...).lower()
       if ques == "no":
           r = False

which avoids useless recursion issues.

Have a nice day :)