import urllib2

 import re

 import urlparse

 import robotparser

 import datetime

 import time

 class Throttle:

     """

     Add a delay to the same domain between two download

     """

     def __init__(self, delay):

         #  amount of delay between download of a domain

         self.delay = delay

         #  timestamp of when a domain was last accessed

         self.domains = {}

     def wait(self, url):

         domain = urlparse.urlparse(url).netloc

         last_accessed = self.domains.get(domain)

         if self.delay > 0 and last_accessed is not None:

             sleep_sec = self.delay - (datetime.datetime.now() - last_accessed).seconds

             if sleep_sec >= 0:

                 time.sleep(sleep_sec)

                 print 'sleep: ', sleep_sec, 's'

         self.domains[domain] = datetime.datetime.now()

 def download(url, proxy, user_agent='wawp', num_retries=2):

     print 'Downloading:', url

     headers = {'User-agent': user_agent}

     request = urllib2.Request(url, headers=headers)

     opener = urllib2.build_opener()

     if proxy:

         proxy_param = {urlparse.urlparse(url).scheme: proxy}

         opener.add_handler(urllib2.ProxyHandler(proxy_param))

     try:

         html = opener.open(request).read()

     except urllib2.URLError as e:

         print 'Downloading error:', e.reason, '\n'

         html = ''

         if num_retries > 0:

             if hasattr(e, 'code') and 500 <= e.code < 600:

                 return download(url, proxy, user_agent, num_retries - 1)

     return html

 def get_links(html, regstr=r'http:\/\/[^w].*\.tuniu\.com'):

     reg = regstr

     rexp = re.compile(reg)

     return re.findall(rexp, html)

 def deduplicate_list(inputList):

     new_list = []

     for x in inputList:

         if x not in new_list:

             new_list.append(x)

     return new_list

 def crawl_sitemap(url):

     sitemap = download(url)

     links = get_links(sitemap)

     print 'before links are : ', links

     newlinks = deduplicate_list(links)

     print 'after links are : ', newlinks

     for link in newlinks:

         print link

         download(link)

 def get_robot(url):

     rp = robotparser.RobotFileParser()

     rp.set_url(urlparse.urljoin(url, 'robots.txt'))

     rp.read()

     return rp

 def link_crawler(seed_url, max_depth=3, link_regex=r'http:\/\/[^w][^"]*\.tuniu\.com', delay=1, proxy=None):

     # For robots.txt check install

     rp = get_robot(seed_url)

     # init vars

     throttle = Throttle(delay)

     crwal_queue = [seed_url]

     seen = {seed_url: 0}

     while crwal_queue:

         url = crwal_queue.pop()

         depth = seen[url]

         if depth != max_depth:

             if rp.can_fetch('heimaojingzhang', url):  # here just for joking

                 throttle.wait(url)

                 html = download(url, proxy)

                 #  print 'down func ', url

                 for link in get_links(html, link_regex):

                     link = urlparse.urljoin(seed_url, link)

                     if link not in seen:

                         seen[link] = depth + 1

                         crwal_queue.append(link)

             else:

                 print 'Blocked by robot.txt ', url

 # TODO:

 # fix bugs: (in regex) done on : 2017/09/23 23:16

 # delay: done on : 2017/09/24 21:36

 # proxy

 # depth: done on : 2017/09/23 23:10

 if __name__ == '__main__':

     link_crawler('http://www.tuniu.com/corp/sitemap.shtml', link_regex=r'http:\/\/www\.tuniu\.com\/guide\/[^"]*')

     #  html = download('http://www.tuniu.com/corp/sitemap.shtml')

     #  print  html