编写Python脚本批量下载DesktopNexus壁纸的教程

DesktopNexus 是我最喜爱的一个壁纸下载网站，上面有许多高质量的壁纸，几乎每天必上， 每月也必会坚持分享我这个月来收集的壁纸

但是 DesktopNexus 壁纸的下载很麻烦，而且因为壁纸会通过浏览器检测你当前分辨率来展示 合适你当前分辨率的壁纸，再加上是国外的网站，速度上很不乐观。

于是我写了个脚本，检测输入的页面中壁纸页面的链接，然后批量下载到指定文件夹中。

脚本使用 python 写的，所以需要机器上安装有 python 。
用法：

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

    -p 包含 DesktopNexus 壁纸链接的页面，比如我的壁纸分享
    -s 壁纸尺寸，可选，缺省为 1440x900
    -o 壁纸输出的文件夹，可选，缺省为当前目录下的 wallpapers， 如果不存在会自动创建

代码：

#-*- 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\/\?t=(?P<token>.*?)\"' ％ 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()