ob-wp-switcher

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# pylint: disable=invalid-name

import os
import sys
import ConfigParser
import Xlib.display
import subprocess

CONFIG_FILE = os.environ['HOME'] + '/.config/openbox/ob-wp-switcher.ini'
TOOL = ["/usr/bin/nitrogen", "--set-scaled"]

if __name__ == '__main__':
    display = Xlib.display.Display()
    screen = display.screen()

    names = screen.root.get_full_property(display.get_atom(
        '_NET_DESKTOP_NAMES'), 0).value.strip('\x00').split('\x00')

    current = screen.root.get_full_property(
        display.get_atom('_NET_CURRENT_DESKTOP'), 0).value[0]

    config = ConfigParser.RawConfigParser()
    if CONFIG_FILE not in config.read(CONFIG_FILE):
        print "could not load config"
        sys.exit(1)

    wallpaper = config.get("main", "base_dir").rstrip("/")
    wallpaper += "/" + config.get("wallpapers", names[current])

    TOOL.append(wallpaper)
    subprocess.check_call(TOOL)

ob-wp-switcher.ini

[main]
base_dir = /home/ephur/Pictures/Background/1440span/

[wallpapers]
Left = 1.jpg
Main = 2.jpg
Right = 3.jpg