Python How to stop a loop with an user input

Question

This is probably a simple answer but I thought I'd ask anyway.

My code below is asking the user for a number and depending on the answer provided will print the grade that corresponds with the numbers.

I want to stop the loop (terminate the program) by having the user type in (999). I know the problem is in my if userScore >= 90" print ('A') . So when the user enters the 999, the computer takes it as an A.

Is there a shortcut to fix this?

(PS I added the breaks to every line because when they were not there the outputs kept repeating endlessly.)

    userScore = float(input('Enter the score or type "999" to quit: '))

    while True:

        try:
            if userScore >= 90:
                print ("You earned an A")
                break


            elif userScore >= 80:
                print ("You earned a B")
                break


            elif userScore >= 70:
                print ("You earned a C")
                break


            elif userScore >= 60:
                print ("You earned a D")
                break


            elif userScore <= 59.9:
                print ("You earned an F")
                break

        except:
            if userScore == '999':
                break
          main()

Answer 1

Don't use try except. Try except is meant for error handling. This can be handled using a simple while loop.

userScore = float(input('Enter the score or type "999" to quit: '))

while userScore!=999:
    if userScore >= 90:
        print ("You earned an A")
        break

    elif userScore >= 80:
        print ("You earned a B")
        break

    elif userScore >= 70:
        print ("You earned a C")
        break

    elif userScore >= 60:
        print ("You earned a D")
        break

    elif userScore <= 59.9:
        print ("You earned an F")
        break
main()  # Why is this even required?

Answer 2

Here is what you are trying to accomplish. It is explained in the comments.

while True:

    #This part gets the user input.  It waits until the user enters a valid number input.
    while True:
        prelim = input('Enter the score or type "999" to quit: ')
        try:
            prelim = int(prelim)
        except:
            print("Please enter a valid input.")
        else:
            #if the input can be converted into a number, then this is our final input value
            userScore = float(prelim)
            break

    #The first thing we should check is if the user wants to exit.  This way it won't print out an answer then exit.
    if userScore == 999:
        break

    if userScore >= 90:
        print ("You earned an A")


    elif userScore >= 80:
        print ("You earned a B")


    elif userScore >= 70:
        print ("You earned a C")


    elif userScore >= 60:
        print ("You earned a D")


    elif userScore <= 59.9:
        print ("You earned an F")