Question

I was writing a little program that takes a list and generates a menu out of it in curses (straight up, standard library or whatever, batteries included python’s curses) when I noticed the strangest problem (if you’d like, a heavily commented copy of the entire program is below). Simply put, when accepting the results of an os.listdir generated list, curses crashes with an addstr ERR, BUT, if I feed it a hardcoded list, it works fine. This, of course, makes absolutely no sense, right? A list is a list is a list and a list by any other name should still be a list, right?

To make things even more complicated, I sent the code to a friend of mine who works mainly in python2.6 (mine was originally written to work in python3.1). He uncommented the broken_input() call (which feeds the program the os.listdir generated information) and said that it worked fine for him. I have both python 2.6 and 3.1 installed, so I changed my shebang to make the program run in 2.6, and (with the broken_input() uncommented) for me, it still throws the addstr ERR (yet runs fine with the hardcoded input… which is, of course, btw, entirely useless apart from proof of concept).

Thus, my question is this: is there something broken in my python installation (I’m running Ubuntu lucid, with python2.6.5 and 3.1 installed), and, if so, how do I fix it so I can get curses to execute this code properly. And, if it’s not my python installation, how can I get the same functionality out of curses (i.e.: paint a menu from a list containing an arbitrary number of items, numbering them so that the user can make a selection based on the item number).

#!/usr/bin/env python3.1
"""curses_mp3eater.py: a curses-based implementation of my mp3eater program;
diplays the contents of cwd, allows user to make a selection. But I'm having
problems getting it to iterate over a list.
v0.1 03.14.11
by skookie sprite
[e-mail]
"""

import curses, curses.wrapper, os, sys


def working_input():
    """the following is demo code to demonstrate my problem... main will accept the following,
    but won't accept the product of a directorylist for reasons that I can't figure out."""
    dircontents=['this','is','a','list','','and','it','will','iterate','fine','in','the','(main) function.']
    return dircontents

def broken_input():
    """this is the code that I NEED to have work... but for reasons beyond me will not iterate in
    the main function. It's a simple list of the contents of the CWD."""
    cwd=os.getcwd()
    dircontents=[]
    for item in os.listdir(cwd):
        dircontents += [item]
    return dircontents

def main(stdscr):
    """This is the program. Designed to take a list of stuff and display it. If I can solve
    that hurdle, I'll add selection mechanisms, and break it across screens - amongst other
    things. But, currently, it can only accept the demo code. Uncomment one or the other to
    see what I mean."""
    #broken_input returns an addstr() ERR, but I don't see the difference between working_input
    #and broken_input as they are both just lists. 
    #working_input() is demo code that illustrates my problem
    stuffin=working_input()
    #stuffin=broken_input()

    #the rest of this stuff works. The problem is with the input. Why?
    linenumber=int()
    linenumber=6
    itemnumber=int()
    itemnumber=1

    stdscr.clear()
    stdscr.border(0)

    for item in stuffin:
        stdscr.addstr(linenumber, 10, '%s   -   %s' % (itemnumber, item), curses.A_NORMAL)
        linenumber += 1
        itemnumber += 1

    curses.doupdate()
    stdscr.getch()



if __name__ == '__main__':
    curses.wrapper(main)

Answer 1

You’re stuffing too much onto the screen and thus passing an out-of-bounds line number to addstr. If you make an empty directory to run the program in (or enlarge your terminal window), it works.

To fix this, check the number of lines in the window before the output loop in main.