While loop continues infinitely even after condition is satisfied

Question

Here is a loop to make sure players of my small game input valid answers but the while loop conintues infinitely, even when the conditions are satisfied to break the loop:

initialize = ''
    while initialize != 'yes' or initialize != 'no':
        print('\nWould you like to play?')
        initialize = input('Yes or No? ').lower().strip()
        if initialize == 'yes':
            print('\nHappy to see you.\n')
        elif initialize == 'no':
            print('\nNo worries.\n\nThanks for stopping by!') 
        else:
            print('\nSorry, I didn\'t catch that')
print('please wait as game loads')
print('\nYou\'re very important to us\n')

if 'yes' or 'no' is typed in the correct if statement runs but the loop continues: Would you like to play? Yes or No? yes

Happy to see you.

Would you like to play? Yes or No?

Your while condition is equivalent to `not (initialize == 'yes' and initialize == 'no')` ([De Morgan's Law](https://stackoverflow.com/a/2168630/4859885)). In this form, it's clear to see why it loops indefinitely. — Brian Rodriguez, Nov 29 '20 at 14:19
Related:[multiple conditions with while loop in python](https://stackoverflow.com/questions/26578277/multiple-conditions-with-while-loop-in-python). — wwii, Nov 29 '20 at 14:48

Aplet123 · Answer 1 · 2020-11-29T14:55:37.067

4

You don't want or, you want and, since it will always be unequal to one of the two:

initialize = 'yes' # start it off with something valid so the loop runs
while initialize != 'yes' and initialize != 'no':
    print('\nWould you like to play?')
    initialize = input('Yes or No? ').lower().strip()
    if initialize == 'yes':
        print('\nHappy to see you.\n')
    elif initialize == 'no':
        print('\nNo worries.\n\nThanks for stopping by!') 
    else:
        print('\nSorry, I didn\'t catch that')

Alternatively, use not in:

while initialize not in ['yes', 'no']:
    # code goes here

edited Nov 29 '20 at 14:55

answered Nov 29 '20 at 14:15

Aplet123

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I wanted to comment this answer just now, but you did it first so I'm upvoting your answer. – Navaneeth Reddy Nov 29 '20 at 14:16

score 0 · Answer 2 · answered Nov 29 '20 at 14:24

Very quick and dirty hack

initialize = ''


while initialize == '':
    print('\nWould you like to play?')
    initialize = input('Yes or No? ').lower().strip()
    if initialize == 'yes':
        print('\nHappy to see you.\n')
    elif initialize == 'no':
        print('\nNo worries.\n\nThanks for stopping by!')
    else:
        print('\nSorry, I didn\'t catch that')
        
print('please wait as game loads')
print('\nYou\'re very important to us\n')

The problem with your code was that the evaluation in the while bit is wrong.

While loop continues infinitely even after condition is satisfied

2 Answers2