Python Login

    def enterDetails(users, passwords):
        #Another definition
        global enterUser
        #Another global variable
        userAlready = messagebox.askyesno("Account?","Do you already have an account?")
        #Creates a message box asking if they have got an account, returning a boolean
        if userAlready == True:
            #If the user presses 'Yes'...
            enterUser = input("Enter your username\n> ").lower()
            #Gets the username and puts it in lower case
            if enterUser in users:
                #if the user is in the users.txt document...
                enterPass = str(input("Enter your password\n> "))
                #Gets the password
                userPos = users.index(enterUser)
                #Creates a variable and stores the number of lines in users
                if enterPass in passwords:
                    #if the passwrod entered is in pass.txt...
                    passPos = passwords.index(enterPass)
                    #indexes the passwords
                    if userPos == passPos:
                        #if the 2 numbers are the same
                        print ("You have successfully logged in", enterUser)
                        time.sleep(5)
                        clear()
                        #log them in
                        return True
                    #moves on to the next definition
                    else:
                        #else...
                        print("You have entered the wrong password, please try again!")
                        #if the password was wrong, ask them to re enter the user and password and restarts program
                        time.sleep(5)
                        clear()
                else:
                    #else...
                    print("We couldn't find your password, please try again!")
                    #if the password isn't in pass.txt, ask them to re enter user and password and resets program
                    time.sleep(5)
                    clear()
            else:
                #else...
                retryUser = messagebox.askyesno("Retry?","We couldn't find your username, would you like to retry?")
                #asks them if they want to try another username
                if retryUser == True:
                    #if they do...
                    i = 0
                    #returns i as 0, restarting the loop
                    time.sleep(5)
                    clear()
                else:
                    #else...
                    quit()
                    #it quits the program
            return False
        #returns false (I believe this is obselete)
        else:
            #else if they don't have a user
            file = open('users.txt','a')
            #open users.txt as 'amend'
            newUser = input("Please enter username\n").lower()
            #asks for a new username and puts it in lower case
            file.write("\n" + newUser)
            #writes the new user on a new line
            file.close()
            #closes the file

            f = 0
            #defines f as 0
            while f == 0:
                #creates a loop
                file = open('pass.txt','a')
                #opens pass.txt as 'amend'
                newPass = input("Please enter password\n")
                #asks for a new password
                confirmPass = input("Please confirm password\n")
                #asks for comformation
                if newPass == confirmPass:
                    #if they are the same...
                    file.write("\n" + newPass)
                    #write the password to the file
                    file.close()
                    #close the file
                    print("New user created! Please restart the program and log in with your credidentials")
                    #prints text
                    quit()
                    #quits the program
                else:
                    #else...
                    print("Passwords didn't match, please try again or use a different password.")
                    #tells them the passwords don't match and restarts the password loop
                    f == 0
                    time.sleep(5)
                    clear()
                    #sets f to 0