How to create a menu and submenus in Python curses?

    0. top
    1. Exit
    2. Another menu
-- end of the old menu that should go away --
    3. first
    4. second
    5. third

#!/usr/bin/python
#
# Adapted from:
# http://blog.skeltonnetworks.com/2010/03/python-curses-custom-menu/
#
# Goncalo Gomes
# http://promisc.org
#

import signal
signal.signal(signal.SIGINT, signal.SIG_IGN)

import os
import sys
import curses
import traceback
import atexit
import time

import sys
reload(sys)
sys.setdefaultencoding("utf-8")

class cmenu(object):
    datum = {}
    ordered = []
    pos = 0

    def __init__(self, options, title="python curses menu"):
        curses.initscr()
        curses.start_color()
        curses.init_pair(1, curses.COLOR_RED, curses.COLOR_WHITE)
        curses.curs_set(0)
        self.screen = curses.initscr()
        self.screen.keypad(1)

        self.h = curses.color_pair(1)
        self.n = curses.A_NORMAL

        for item in options:
            k, v = item.items()[0]
            self.datum[k] = v
            self.ordered.append(k)

        self.title = title

        atexit.register(self.cleanup)

    def cleanup(self):
        curses.doupdate()
        curses.endwin()

    def upKey(self):
        if self.pos == (len(self.ordered) - 1):
            self.pos = 0
        else:
            self.pos += 1

    def downKey(self):
        if self.pos <= 0:
            self.pos = len(self.ordered) - 1
        else:
            self.pos -= 1

    def display(self):
        screen = self.screen

        while True:
            screen.clear()
            screen.addstr(2, 2, self.title, curses.A_STANDOUT|curses.A_BOLD)
            screen.addstr(4, 2, "Please select an interface...", curses.A_BOLD)

            ckey = None
            func = None

            while ckey != ord('\n'):
                for n in range(0, len(self.ordered)):
                    optn = self.ordered[n]

                    if n != self.pos:
                        screen.addstr(5 + n, 4, "%d. %s" % (n, optn), self.n)
                    else:
                        screen.addstr(5 + n, 4, "%d. %s" % (n, optn), self.h)
                screen.refresh()

                ckey = screen.getch()

                if ckey == 258:
                    self.upKey()

                if ckey == 259:
                    self.downKey()

            ckey = 0
            self.cleanup()
            if self.pos >= 0 and self.pos < len(self.ordered):
                self.datum[self.ordered[self.pos]]()
                self.pos = -1
            else:
                curses.flash()



def top():
    os.system("top")

def exit():
    sys.exit(1)

def submenu():
    # c.screen.clear()     # nope
    # c.cleanup()          # nope
    submenu_list = [{"first": exit}, {"second": exit}, {"third": exit}]
    submenu = cmenu(submenu_list)
    submenu.display()

try:

    list = [{ "top": top }, {"Exit": exit}, {"Another menu": submenu}]

    c = cmenu(list)

    c.display()

except SystemExit:
    pass
else:
    #log(traceback.format_exc())
    c.cleanup()