我该如何修复while循环

Question

I am writing a program that asks the user to enter a password. If the password matches the constant I've set it prints out a "successfully logged in message". However if the password is incorrect, it gives the number of guesses left and asks the user to try again. The program should end after 3 incorrect guesses but it keeps on asking even after 3 attempts have been used. I think the problem is in my while loop but I am unsure.

Code:

def main():
    PASSWORD = "apple"
    ALLOWED = 3

    password = input("Enter the password: ")
    while password != PASSWORD :
        ALLOWED = ALLOWED - 1
        print("Wrong. You have", ALLOWED, "guesses left")

        if ALLOWED == 0:
                    print("You have been locked out")
        password = input("Enter again ")            


    print("You have successfully logged into the system")



main()

Answer 1

Right now you never exit your while loop. To break out of it, use the break keyword. To exit your program completely, you will need to import sys and sys.exit() I suggest adding these to your if ALLOWED == 0 statement.

Answer 2

You need to use break to exit the loop, or add a secondary condition, otherwise it will keep going anyway until the password is correct.

So, either:

while (password != PASSWORD) and (ALLOWED > 0):

Or:

    if ALLOWED == 0:
                print("You have been locked out")
                break

Answer 3

The condition password != PASSWORD is not enough to exit the loop (It will exit the loop only if you give the right password). Add the condition also in while (password != PASSWORD and ALLOWED > 0)

Answer 4

Change print("You have been locked out") to sys.exit("You have been locked out") (or otherwise exit the main ). Remember to import sys to use sys.exit .

Answer 5

Your while loop requires a correct password to finish, and there is no other way to exit the loop. I suggest a break statement:

def main():
    PASSWORD = "apple"
    ALLOWED = 3

    password = input("Enter the password: ")
    while password != PASSWORD :
        ALLOWED = ALLOWED - 1
        print("Wrong. You have", ALLOWED, "guesses left")

        if ALLOWED == 0:
            print("You have been locked out")
            break
        password = input("Enter again ")

    print("You have successfully logged into the system")

You may want to do more research if your program needs to be secure.

Answer 6

Managed to make it work but just making it check if ALLOWED == 0 and if it does print "you are locked out", and if ALLOWED <= 0 then it will not let you go any further.

def main():
    PASSWORD = "apple"
    ALLOWED = 3

    password = input("Enter the password: ")
    while password != PASSWORD or ALLOWED <= 0:
        ALLOWED = ALLOWED - 1
        if ALLOWED > 0: print("Wrong. You have", ALLOWED, "guesses left")
        if ALLOWED == 0: print("You have been locked out") 
        if ALLOWED < 0:
                    print("You have been locked out")
        password = input("Enter again ")            


    print("You have successfully logged into the system")



main()

also wrote a different version which seemed easier in my opinion

def main():

    USERNAME = "admin"
    PASSWORD = "root"
    ATTEMPTS = 3
    while ATTEMPTS >= 1:
        print("You have",ATTEMPTS,"attempts left")
        if ATTEMPTS == 0:
            break
        user = input("Please enter your username:")
        password = input("Now enter your password:")
        if user == USERNAME and password == PASSWORD:
            print("\nYou have successfully logged into the system")
            return
        else:
            print("\nThis user name or password does not exist\n")
            ATTEMPTS -= 1
    print("you have been locked out.")

main()