$ python desktop_nexus.py -p http://www.desktopnexus.com/tag/cat/ -s 1280x800 -o wallpapers

#-*- coding: utf-8 -*-
from argparse import ArgumentParser

import os, re, sys
import urllib2, cookielib, urlparse

RE_WALLPAPER = r'http\:\/\/[^\/\.]+\.desktopnexus\.com\/wallpaper\/\d+\/'
CHUNK_SIZE = 1024 * 3

class DesktopNexus:
  def __init__(self, page=None, size=None, output_dir=None):
    self.page = page
    self.size = size
    self.output_dir = output_dir

  def start(self):
    print 'Making output directory:', self.output_dir
    if not os.path.exists(self.output_dir):
      os.makedirs(self.output_dir)

    # Setup cookie
    cookie = cookielib.CookieJar()
    processer = urllib2.HTTPCookieProcessor(cookie)
    opener = urllib2.build_opener(processer)
    urllib2.install_opener(opener)

    self._read_page()

  def _get_pic_info(self, url):
    pic_id = url.split('/')[-2]
    html = urllib2.urlopen(url).read()
    pattern = r'<a href=\"\/get\/%s\/\"' % pic_id
    match = re.search(pattern, html, flags=re.I|re.M|re.S)
    if match:
      return {'id': pic_id,
          'token': match.group('token'),
          'size': self.size}
    else:
      raise Exception('Cound not find wallpaper')

  def _get_pic_file(self, pic_info):
    redirect_url = 'http://www.desktopnexus.com/dl/inline/%(id)s/%(size)s/%(token)s' % pic_info

    request = urllib2.urlopen(redirect_url)
    return request.geturl()

  def _download_pic(self, url):
    pic_info = self._get_pic_info(url)
    pic_file = self._get_pic_file(pic_info)
    filename = os.path.split(urlparse.urlparse(pic_file).path)[-1]
    filename = os.path.join(self.output_dir, filename)
    with open(filename, 'wb') as output:
      resp = urllib2.urlopen(pic_file)
      total_size = int(resp.info().get('Content-Length'))
      saved_size = 0.0
      while saved_size != total_size:
        chunk = resp.read(CHUNK_SIZE)
        saved_size += len(chunk)
        output.write(chunk)
        self._print_progress('Saving file: %s' % filename,             saved_size / total_size * 100)

  def _print_progress(self, msg, progress):
    sys.stdout.write('%-71s%3d%%\r'         % (len(msg) <= 70 and msg or msg[:67] + '...', progress))
    sys.stdout.flush()
    if progress >= 100:
      sys.stdout.write('\n')

  def _read_page(self):
    try:
      print 'Fetching content:', self.page
      html = urllib2.urlopen(self.page).read()
      links = set(re.findall(RE_WALLPAPER, html, re.M|re.I))
      count = len(links)

      print 'Downloading wallpapers:'
      for i, link in enumerate(links):
        print '[%d/%d]: %s' % (i + 1, count, link)
        try:
          self._download_pic(link)
        except Exception as e:
          print 'Error downloading wallpaper.', e.message
    except Exception as e:
      print 'Error fetching content.', e

if __name__ == '__main__':
  # Setup argparser
  parser = ArgumentParser('python desktop_nexus.py')
  parser.add_argument('-p', '--page', dest='page', required=True,       help='specific a page that includes wallpaper list')
  parser.add_argument('-s', '--size', dest='size', default='1440x900',       help='specific the wallpaper size, default to 1440x900')
  parser.add_argument('-o', '--output', dest='output_dir', default='wallpapers',       help='specific the output directory, default to "wallpapers"')
  args = parser.parse_args()
  dn = DesktopNexus(**args.__dict__)
  dn.start()