Python while loop condition check for string

Question

In Codeacademy, I ran this simple python program:

choice = raw_input('Enjoying the course? (y/n)')

while choice != 'y' or choice != 'Y' or choice != 'N' or choice != 'n':  # Fill in the condition (before the colon)
    choice = raw_input("Sorry, I didn't catch that. Enter again: ")

I entered y at the console but the loop never exited

So I did it in a different way

choice = raw_input('Enjoying the course? (y/n)')

while True:  # Fill in the condition (before the colon)
    if choice == 'y' or choice == 'Y' or choice == 'N' or choice == 'n':
        break
    choice = raw_input("Sorry, I didn't catch that. Enter again: ")

and this seems to work. No clue as to why

Answer 1

You have your logic inverted. Use and instead:

while choice != 'y' and choice != 'Y' and choice != 'N' and choice != 'n':

By using or , typing in Y means choice != 'y' is true, so the other or options no longer matter. or means one of the options must be true, and for any given value of choice , there is always at least one of your != tests that is going to be true.

You could save yourself some typing work by using choice.lower() and test only against y and n , and then use membership testing:

while choice.lower() not in {'n', 'y'}: