Log sys taceback

"""

    Log in system with a feature of changing username and password

"""


def input_func(part):        # 1, the user will be inputting here the choice of what he want to do.
    if part == 1:            # part 1 == while not logged in | part 2 == while logged in.
        while True:
            choice = input(""""Input the number of your choice:
            1. Sing up
            2. Login
            7. Exit\n""")
            try:
                choice = int(choice)

            except ValueError:
                print('Input the number of your choice')
                continue

            if choice == 1 or choice == 2 or choice == 7:
                break

            else:
                print('Invalid number')
                continue

        return choice

    if part == 2:
        while True:
            choice2 = input(""""Input the number of your choice:
            3. Change password
            4. Change username
            5. Logout
            7. Exit\n""")
            try:
                choice2 = int(choice2)

            except ValueError:
                print('Input the number of your choice')
                continue

            if choice2 == 3 or choice2 == 4 or choice2 == 5 or choice2 == 7:
                break

            else:
                print('Invalid number')
                continue

        return choice2


def sign_up_system():    # 2, function that responsible for the signing up.
    user_name = input('Input Username: ')
    password = input('Input password: ')
    return user_name, password


def change_pass():       # 3, function that changes your pass.
    new_pass = input('Type your new password: ')
    print('Your new password is: '), new_pass
    return new_pass


def change_usrname():    # 4, function that changes your user name.
    new_username = input('Type your new password: ')
    print('Your new password is: ', new_username)
    return new_username


def users_storage(part, users_name, users_pass, old_user):       # 5, checks if the user and pass are valid.
                                    # part 1 == the sign up | part 2 == login check | part 3 == change pass | part 4 == change username
    users_storage = {}
    if part == 1:
        users_storage[users_name] = users_pass

    elif part == 2:
        if users_storage[users_name] == users_pass:
            return True
        else:
            return False

    elif part == 3:
        users_storage[users_name] = users_pass

    elif part == 4:
        users_storage[users_name] = users_storage.pop(old_user)


def main():              # The main function that includes everything and runs the program.
    print("Hi welcome to the Login system\n")
    done = False
    while not done:
        logged_in = False
        while not logged_in:
            choice = input_func(1)

            if choice == 1:  # Sign up
                sign_up_user_name, sign_up_user_pass = sign_up_system()
                users_storage(1, sign_up_user_name, sign_up_user_pass, None)

            elif choice == 2:
                login_check = False
                while not login_check:  # Log in checks checks if the user and pass are valid or not.
                    log_in_user_name = input('Username: \n')
                    log_in_user_pass = input('Password: ')

                    login_check = users_storage(2, log_in_user_name, log_in_user_pass, None)

                    if login_check == False:
                        'Invalid username or password'

                    elif login_check == True:
                        logged_in = True

            elif choice == 7:  # Exit
                done = True

        while logged_in:
            choice2 = input_func(2)  # input function part 2

            if choice2 == 3:  # change password
                new_pass = change_pass()
                users_storage(3, log_in_user_name, new_pass, None)

            elif choice2 == 4:  # Change username
                new_username = change_usrname()
                users_storage(4, new_username, log_in_user_pass, log_in_user_name)

            elif choice2 == 5:  # Logout
                logged_in = False

            elif choice2 == 7:  # Exit
                done = True


if __name__ == '__main__':
    main()



TRACEBACK:
Hi welcome to the Login system

"Input the number of your choice:
            1. Sing up
            2. Login
            7. Exit
1
Input Username: j
Input password: j
"Input the number of your choice:
            1. Sing up
            2. Login
            7. Exit
2
Username:
j
Password: j
Traceback (most recent call last):
  File "C:/untitled/Projects/Login syste,/log_in.py", line 140, in <module>
    main()
  File "C:/untitled/Projects/Login syste,/log_in.py", line 110, in main
    login_check = users_storage(2, log_in_user_name, log_in_user_pass, None)
  File "C:/untitled/Projects/Login syste,/log_in.py", line 80, in users_storage
    if users_storage[users_name] == users_pass:
KeyError: 'j'

Process finished with exit code 1