Grabs a random wallpaper from the wallbase.net toplist.

randwp.py

#!/usr/bin/env python
"""
    randwp
    ~~~~~~

    Fetches random wallpapers from the wallbase.net toplist and sets it as the
    background.

    This script needs Python 3.*. Windows people need to install the `pywin32`_
    and Mac OS X people need to install `py-appscript`_.

    .. _pywin32: http://sourceforge.net/projects/pywin32/
    .. _py-appscript: http://appscript.sourceforge.net/py-appscript/index.html

    :copyright: (c) 2010 by Frank Smit.
    :license: BSD, see LICENSE for more details.
"""

__author__ = 'Frank Smit'
__version__ = '0.1.0'


import re
import sys
import json
import shlex
import random
import os.path
import subprocess
import urllib.parse
import urllib.request
from os.path import basename
from optparse import OptionParser


# Platform specific stuff
if sys.platform == 'win32':
    import win32api, win32con, win32gui
    DATA_DIR = os.path.join(os.getenv('AppData'), 'randwp')
elif sys.platform == 'darwin':
    import appscript
    DATA_DIR = os.path.join(os.path.expanduser('~'), '.randwp')
else:
    DATA_DIR = os.path.join(os.getenv('XDG_DATA_HOME',
        os.path.expanduser('~/.local/share')), 'randwp')


REGEX_IMAGE = re.compile("(http:\/\/wallbase2\.org\/[a-zA-Z0-9_-]+\/"
                         "[a-zA-Z0-9]+\/wallpaper-[0-9]+\.(?:jpg|png))")

PAGE_LIMIT = 325
THUMBS_PER_PAGE = 60
RESOLUTIONS = (
    '0x0', # Everything

    # Standard
    '800x600',   '1024x768',
    '1280x960',  '1280x1024',
    '1400x1050', '1600x1200',
    '2560x2048',

    # Widescreen
    '1024x600',  '1280x800',
    '1366x768',  '1440x900',
    '1600x900',  '1680x1050',
    '1920x1080', '1920x1200',
    '2560x1440', '2560x1600'
)
ASPECT_RATIOS = {
    'all': '0', # All aspect ratios
    '4:3': '1.33',
    '5:4': '1.25',
    '16:9': '1.77',
    '16:10': '1.60',
    'netbook': '1.70',
    'dual': '2.50',
    'dual_wide': '3.20',
    'portrait': '0.99'
}

WB_OVERVIEW_URL = 'http://wallbase.cc/toplist/%(page)s/%(boards)s/%(size)s/' \
    '%(resolution)s/%(aspect_ratio)s/%(level)s/%(thumbs)s'
WB_WP_URL = 'http://wallbase.cc/wallpaper/%d'


class Grabber:
    """A simple class that grabs a random wallpaper from wallbase.net

    :param url: The URL to a wallbase.net gallery.
    """
    def __init__(self, url, callback):
        wpid = []
        json_data = self._get_json(url)
        if json_data:
            for data in json_data:
                wpid.append(data['id'])

            wallpaper_url = self._get_wallpaper_url(
                WB_WP_URL % random.choice(wpid))

            if wallpaper_url:
                path = self._download_wallpaper(wallpaper_url)
                callback(path)
        else:
            print('Could not find wallpapers!')

    def _get_json(self, url):
        req = urllib.request.Request(url, b'', {
            'x-requested-with': 'XMLHttpRequest',
            'Cookie': 'is_adult=1'
        })
        response = urllib.request.urlopen(req)
        data = response.read().decode('utf-8')

        try:
            return json.loads(data)
        except ValueError:
            return []

    def _get_wallpaper_url(self, url):
        response = urllib.request.urlopen(url)
        html = response.read().decode('utf-8')

        matches = REGEX_IMAGE.search(html)
        if matches:
            return matches.group(1)

    def _download_wallpaper(self, url):
        path = os.path.join(DATA_DIR, basename(url))
        if os.path.exists(path):
            return path

        return urllib.request.urlretrieve(url, path)[0]


class BackgroundSetter(object):
    """A simple background setter. At this moment is only accepts a CLI command.
    More options are planned in the future.

    :param command: The CLI command. %(path)s is replaced with the path to
                    the wallpaper, which is saved in ``~/.local/share``.
    """
    def __init__(self, command):
        self.setters = {
            'win32': self._win32_setter,
            'macosx': self._mac_osx_setter
        }
        self.command = command

    def set(self, path):
        """Sets the wallpaper to the background by executing the CLI command.

        :param path: The path to the wallpaper.
        """
        if self.command in self.setters:
            self.command = self.setters[self.command](path)
        else:
            self.command = self._cli_setter(path)

    def _cli_setter(self, path):
        subprocess.call(shlex.split(self.command.replace('%path%', path)))

    # Source: http://www.daniweb.com/code/post969627.html
    def _win32_setter(self, path):
        key = win32api.RegOpenKeyEx(win32con.HKEY_CURRENT_USER,
            'Control Panel\\Desktop', 0, win32con.KEY_SET_VALUE)
        win32api.RegSetValueEx(key, 'WallpaperStyle', 0, win32con.REG_SZ, '0')
        win32api.RegSetValueEx(key, 'TileWallpaper', 0, win32con.REG_SZ, '0')
        win32gui.SystemParametersInfo(win32con.SPI_SETDESKWALLPAPER, path, 1+2)

    def _mac_osx_setter(self, path):
        appscript.app('Finder').desktop_picture.set(
            appscript.mactypes.File(path))


def main():
    if not os.path.exists(DATA_DIR):
        os.makedirs(DATA_DIR)

    # Set up CLI arguments parser and CLI options
    opt = OptionParser()

    opt.add_option('-s', '--bg-setter', dest='setter',
        help='Set a background setter. Available values: win32, macosx. '
             'When no suitable value is available a CLI command can be used. '
             'Example: randwp.py -s \'feh --bg-tile "%path%"\'. %path% will '
             'be replaced with the path to the wallpaper.',
        metavar='BGSETTER')

    opt.add_option('--gt', action='store_true', dest='gt',
        default=False, help='Use wallpapers with the specified resolution or '
                            'greater.')

    opt.add_option('-p', '--page', dest='page',
        help='The pagenumber of the results from wallbase.net. A range can '
             'also be used. Examples: 1..5, 5..10, etc. The first number can '
             'not be zero. And the last number must be higher than the first '
             'one.',
        metavar='PAGE', default='1')

    opt.add_option('--no-w', action='store_false', dest='w', default=True,
        help='No wallpapers from /W/ (Manga / Anime).')
    opt.add_option('--no-wg', action='store_false', dest='wg', default=True,
        help='No wallpapers from /WG/ (Wallpapers / General).')
    opt.add_option('--no-hr', action='store_false', dest='hr', default=True,
        help='No wallpapers from /HR/ (High Resolution. Contains not only '
             'wallpapers, but also other high-res pictures).')

    opt.add_option('-r', '--resolution', dest='resolution',
        help='Specify a resolution (default is 0x0): %s' % \
            ', '.join(RESOLUTIONS),
        metavar='RESOLUTION', default='0x0')

    opt.add_option('-a', '--aspect-ratio', dest='aspect_ratio',
        help='Specify an aspect ratio (default is all): %s' % \
            ', '.join(ASPECT_RATIOS.keys()),
        metavar='ASPECT_RATIO', default='all')

    opt.add_option('--no-sfw', action='store_false', dest='sfw', default=True,
        help='Don\'t use Safe For Work wallpapers.')
    opt.add_option('--sketchy', action='store_true', dest='sketchy',
        default=False, help='Sketchy wallpapers.')
    opt.add_option('--nsfw', action='store_true', dest='nsfw', default=False,
        help='Not Safe For Work wallpapers.')

    opt.add_option('--clear-cache', action='store_true', dest='clear',
        default=False, help='Clear all the cached wallpapers.')

    (options, args) = opt.parse_args()

    # Check for a background setter
    if not options.setter:
        print('A background setter must be specified.')
        sys.exit()

    # Clear cache and exit
    if options.clear:
        for f in os.listdir(DATA_DIR):
            os.remove(os.path.join(DATA_DIR, f))
        os.rmdir(DATA_DIR)
        sys.exit()

    # Check page range or number
    p_range_match = re.match('([1-9]|[0-9]{2,})\.\.([0-9]+)', options.page)
    if p_range_match:
        ps, pr = p_range_match.groups()
        ps, pr = int(ps), int(pr)
        if pr < ps:
            print('Invalid page range!')
            sys.exit()
        options.page = random.randint(ps, pr)
    else:
        try:
            options.page = int(options.page)
        except ValueError:
            print('Invalid page number!')
            sys.exit()

    # Check page limit
    if options.page > PAGE_LIMIT:
        print('Page number exceeds page limit (%d)!' % PAGE_LIMIT)
        sys.exit()

    # Check which boards to use
    boards = '%s%s%s' % (
        options.w and '1' or '',
        options.wg and '2' or '',
        options.hr and '3' or ''
    )

    # Check resolution
    if not options.resolution in RESOLUTIONS:
        options.resolution = '0x0'

    # Check aspect ratio
    if not options.aspect_ratio in ASPECT_RATIOS:
        options.aspect_ratio = 'all'

    # Set level (SFW, Sketchy, NSFW)
    level = '%d%d%d' % (int(options.sfw), int(options.sketchy),
        int(options.nsfw))

    setter = BackgroundSetter(options.setter)
    Grabber(WB_OVERVIEW_URL % {
        'page': (options.page - 1) * THUMBS_PER_PAGE,
        'boards': boards,
        'size': options.gt and 'gteq' or 'eqeq',
        'resolution': options.resolution,
        'aspect_ratio': ASPECT_RATIOS[options.aspect_ratio],
        'level': level,
        'thumbs': THUMBS_PER_PAGE
    }, setter.set)


if __name__ == '__main__':
    main()

Ok. I'll do some tests.