Help please: WHILE LOOPS with BOOLEAN LOGIC

[rbulmerstlouis]

Dear all
Why does this code not work when the correct combination of username and password are entered?

username = input("Enter your Username: ")
password = input("Enter your Password: ")

while (username != "Jack" and password != "123") or (username != "Jill" and password != "345"):
          username = input("Enter your Username: ")
          password = input("Enter your Password: ")

print (".....Entering the System")

Yoriz write Jun-20-2021, 10:23 AM:
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[Yoriz]

If one of your combinations of username and password is True the other combination will be False.
When using or x or y, if x is false, then y, else x
So your statement is the equivalent of

print(True or False)
print(False or True)

Which will always be True

Output:
True
True

[jefsummers]

Python's dictionary structure fits well with the task of usernames and passwords. Dictionaries work with key:value pairs
Restructuring, and not limiting you to 2 names:

pasta = False #would have used pass but that is a reserved word
codes = {'Jack':'123', 'Jill':'345'} #Dictionary of the users and pwds 

while not pasta:
    username = input("Enter your Username: ")
    password = input("Enter your Password: ")
    if username in codes.keys(): #Make sure username in the list
        if codes[username] == password: 
            pasta = True
print (".....Entering the System")

Output:
Enter your Username: Fred
Enter your Password: Flintstone
Enter your Username: Jack
Enter your Password: 123
.....Entering the System

[deanhystad]

You need to use and, not or

while (u != u1 and p != p1) and (u != u2 and p != p2):

Which translates to

while login does not match any account

By using or the logic is

while logic does not match all accounts

Avoid duplicate code. Initialize username and password to None and let the first password check fail. The code works the same but is shorter.

If using a dictionary of passwords, use get.

while codes.get(input('Username: ')) != input('Password: '):

[rbulmerstlouis]

Thank you...this is fabulous.
I didn't really want to use Dictionaries, but I can see why you have and see the benefits.

Brilliant :-)