Dice game login system
You are introducing this requirement of not having a password being the same as a username, but the problem is the way you check for it:

create_password = input("enter a new password (Your password cannot be the same as your username !!!!!!!): ")

if create_password in users:


The problem arises when my password matches someone else's username.

I think you meant to just compare create_username with create_password values.



In general, there is rarely a case when you should try writing your own login system except that for learning purposes. You may though improve your current setup by introducing hashing of the passwords, to avoid storing them in plain text: Salt and hash a password in python; as well as more password strength requirements: Checking the strength of a password.