curses: x, y positioning

[7stud]

I can't see to get any y, x coordinates to work with curses.  Here is
an example:

import curses

def my_program(screen):
    while True:
        ch = screen.getch()
        if ch == ord("q"):
            break
        if ch <= 255:
            screen.addstr(30, 10, "*%s*" % chr(ch))
            screen.refresh()

curses.wrapper(my_program)

Here is the result:

Traceback (most recent call last):
  File "2pythontest.py", line 12, in ?
    curses.wrapper(my_program)
  File "/Library/Frameworks/Python.framework/Versions/2.4//lib/
python2.4/curses/wrapper.py", line 44, in wrapper
    return func(stdscr, *args, **kwds)
  File "2pythontest.py", line 9, in my_program
    screen.addstr(30, 10, "*%s*" % chr(ch))
_curses.error: addstr() returned ERR