CODEWITHSUNDEEP
pythonif-statement
user3479466
user3479466

Reputation: 21

Need to know how to loop

This is my first time asking a question on this site so sorry for the minor mistakes.

The question I have is how do I loop the program back to a previous line. I'll be more specific. In the first else statement I made it so that the program ends. I want it to allow the user to have another try at entering the username. How do I do that?

And If you don't understand then please ask me clarify. 

usernames = ("Bob","John","Tyler","Thomas","Sanjit",
             "Super_X","Ronald","Royal_X", "Igor","KoolKid")
passwords = ("James","Smith","Jones","password","Desai",
             "asdf123","Roy","King", "Mad_man", "k00lGuy")

username = raw_input("Enter username")

if username == usernames[0] or username == usernames[1] or username == usernames[2] or \
   username == usernames[3] or username == usernames[4] or username == usernames[5] or \
   username == usernames[6] or username == usernames[7] or username == usernames[8] or \
   username == usernames[9]:
    print "  "
else:
    import sys
    sys.exit("This is not a valid username") 

password = raw_input("Enter Password:")

if username == usernames[0] and password == passwords[0] or \
   username == usernames[1] and password == passwords[1] or \
   username == usernames[2] and password == passwords[2] or \
   username == usernames[3] and password == passwords[3] or \
   username == usernames[4] and password == passwords[4] or \
   username == usernames[5] and password == passwords[6] or \
   username == usernames[6] and password == passwords[7] or \
   username == usernames[7] and password == passwords[8] or \
   username == usernames[9] and password == passwords[9]:
       print "log in successful"
else:
    import sys
    sys.exit("Username and Password do not match.")

Upvotes: 2

Views: 54

Answers (2)

spinlok
spinlok

Reputation: 3661

First off, you'd be better off using a dict to store username and passwords like this:

credentials = {
    "Bob": "James",
     # ....
}

If you want to allow the user 2 tries to get the username right:

for i in xrange(2):
    username = raw_input('Enter username: ')
    if username in credentials:
        break
else:
    print 'username not valid'

The above code uses the for..else construct in python to determine if a break was used to exit the loop. Now, the dict makes it much easier to check if the password was correct:

if password == credentials[username]:
    print 'login successful'

Upvotes: 0

sshashank124
sshashank124

Reputation: 32189

You can do it as follows:

username = ''
while username not in usernames:
    username = raw_input('Enter username: ')

If you want to give them a certain number of tries, you can do:

username = ''
for i in range(3):  #where 3 is the number of tries
    if username not in usernames:
        username = raw_input('Enter username: ')
    else:
        break

and then you can do the same thing for passwords. Hope that helps.

Upvotes: 2

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