Change the Gnome desktop background to a random image from a directory

random_background.py

#!/usr/bin/env python
# This script will change the desktop background to a 
# random image taken from a directory
#
# Use random_background.py --help for options
#
# Author:  Mattijs Hoitink <mattijs@monkeyandmachine.com>
# License: none (public domain)

import sys, argparse, os, mimetypes, re, random, gconf

# Simple argument parsing
parser = argparse.ArgumentParser(description="Change Gnome desktop background to a random image from a directory")
parser.add_argument('--no-recurse', help='If files should not be searched recursively', dest='recursive', action='store_false', required=False)
parser.add_argument('path', action='store', help='Path to the directory to select a wallpaper from')
args = parser.parse_args()

# Check if the path exists
abs_path = os.path.abspath(args.path)
if not os.path.exists(abs_path):
    print "Path '%s' does not exist" % abs_path
    sys.exit(1)

# Find files in a directory recursively (or not)
def find_files(root, recursive = True):
    found = []
    for root, dirs, files in os.walk(root):
        # Append files that are images
        for file in files:
            # Get the file path and mimetype
            filePath = os.path.join(root, file)
            fileMimetype = mimetypes.guess_type(filePath)[0]

            # Check if the found file is an image
            imageRegex = re.compile(r'image/[\w\-\.]*', re.IGNORECASE)
            if fileMimetype and imageRegex.match(fileMimetype):
                found.append(filePath)

        # Check if we need to recurse intor sub-directories
        if recursive:
            for dir in dirs:
                found += find_files(os.path.join(root, dir), recursive)

    return found

# Fetch all wallpapers from the directory
backgrounds = find_files(abs_path, args.recursive)
if 0 >= len(backgrounds):
    print "No background images were found"
    sys.exit(0)

# Modify the background using GConf
gconf_background_path = '/desktop/gnome/background/picture_filename'
client = gconf.client_get_default()

new_background = backgrounds[random.randint(0, len(backgrounds) - 1)]
client.set_string(gconf_background_path, new_background)