menus

x.py

def get_input(valid):
    while True:
        choice = input('->')
        if choice not in valid:
            print('not a valid option')
        else:
            return choice


def menu_one():
    print ("""
----------------------
This is Menu 1.
1. Submenu 1 again
2. Submenu 2
Return to the main menu by typing '0'
----------------------
        """)
    choice = get_input(['0','1','2'])
    if choice == '0':
        return main_menu
    elif choice == '1':
        return menu_one
    elif choice == '2':
        return menu_two
    else:
        print('not implemented yet')

def menu_two():
    print ("""
----------------------
This is Menu 2.
1. Submenu 1
2. Submenu 3
Return to the main menu by typing '0'
----------------------
        """)
    choice = get_input(['0','1','2'])
    if choice == '0':
        return main_menu
    elif choice == '1':
        return menu_one
    else:
        print('not implemented yet')
        return menu_two


def main_menu():
    print ("""
----------------------
This is the main menu:
1. Submenu 1
2. Submenu 2
3. Submenu 2
quit by typing '0'
----------------------
""")
    choice = get_input(['0','1','2','3'])
    if choice == '0':
        return
    elif choice == '1':
        return menu_one
    elif choice == '2':
        return menu_two
    else:
        print('not implemented yet')
        return main_menu

def main():
    current = main_menu
    while True:
        current = current()
        if current is None:
            return

if __name__ == '__main__':
    main()