Curses question

[mike.baranski at gmail.com]

So, can someone tell me why the following code is wrong?

When you run it, it will place a . as you arrow key around the screen.
Everything works, until you get to the bottom right corner of the
screen, trying to move off of this square causes addstr to throw and
exception.

Every other spot works.  Any idea why?

Thanks:

The Code:

#!/usr/bin/python
import curses
import time
import random
import sys

def cleanup():
    curses.nocbreak()
    curses.echo()
    curses.endwin()

    return

def init():
    stdscr = curses.initscr()
    curses.noecho()
    curses.cbreak()
    curses.curs_set(2)
    return

def main():
    pad = curses.newwin(0, 0)
    pad.keypad(0)
    logfile = open('log.txt', 'w')
    # The app goes here...
    direction = 66

    (y, x) = pad.getmaxyx()

    pad.move(0,0)

    while True:
        pad.refresh()
        #    time.sleep(1)

        direction = pad.getch()
#        direction = random.randint(65, 68)
        (cy, cx) = pad.getyx()
        logfile.write("y=%s, x=%s, cy=%s, cx=%s, direction=%s\n" % (y,
x, cy, cx, direction))
        if direction == 65 and cy != 0:
            pad.addstr(".")
            pad.move(cy - 1, cx)
            continue
        elif direction == 66 and cy != y-1:
            pad.addstr(".")
            pad.move(cy + 1, cx)
            continue
        elif direction == 67 and cx != x-1:
            pad.addstr(".")
            pad.move(cy, cx + 1)
            continue
        elif direction == 68 and cx != 0:
            pad.addstr(".")
            pad.move(cy, cx - 1)
            continue
        elif chr(direction) == "q" or chr(direction) == "Q":
            break
        else:
            continue

init()
try:
    main()
except curses.error, e:
    cleanup()
    print "Exception [%s]" % e
    sys.exit()

cleanup()