CODEWITHSUNDEEP
pythonpython-3.x
Vector 2755
Vector 2755

Reputation: 37

having an infinite loop bug on this while loop

empty_Carton = ''

print("Is the milk carton in the fridge empty? y/n")

input(empty_Carton)

while (empty_Carton != 'y') or (empty_Carton != 'n'):
    if empty_Carton == 'y':
        """Branch here"""
    elif empty_Carton == 'n':
        """Branch here"""
    else:
        print(empty_Carton + " is not a valid input. Type: 'y' or 'n'")

When I run this code it enters and infinite loop stuck on the 'else' condition when entering a correct input of 'y'

I tried moving the code around and changing the comparison operator but it still ends up in an infinite loop.

Upvotes: 0

Views: 632

Answers (2)

Himanshu
Himanshu

Reputation: 3970

You have entered the input only once before while loop. Therefore it will run infinite times. Write a function instead and call that function in your else condition or just use a break statement.

empty_Carton = ""

print("Is the milk carton in the fridge empty? y/n") 

while (empty_Carton != 'y') or (empty_Carton != 'n'):
    if empty_Carton == 'y':
        """Branch here"""
    elif empty_Carton == 'n':
        """Branch here"""
    else:
        print(empty_Carton + " is not a valid input. Type: 'y' or 'n'")
        break

Upvotes: -1

Henry Woody
Henry Woody

Reputation: 15652

The first issue is that empty_Carton never gets defined to be anything other than "", you can fix this with:

empty_Carton = input("Is the milk carton in the fridge empty? y/n")

Note that the input function takes a string to print and returns the string entered by the user.

The next issue is that your input call is only made once (above the while loop), so the value of empty_Carton never gets updated and your loop runs forever. Really empty_Carton's value should only get set at the top of the loop so that the loop will execute at least once, but will continue to execute until a valid value is entered.

Finally, since empty_Carton can never be both 'y' and 'n', empty_Carton must always be not equal to at least one of those options, so your while condition is always True. You can fix this by replacing the or with an and, or with:

while empty_Carton not in ('y', 'n'):
    # do stuff

Putting this all together, we get something like:

empty_Carton = ''

while empty_Carton not in ('y', 'n'):
    empty_Carton = input("Is the milk carton in the fridge empty? y/n")
    if empty_Carton == 'y':
        print('y')
    elif empty_Carton == 'n':
        print('n')

Upvotes: 2

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