from baike import url_manager, html_downloader, html_parser, html_outputer


class SpiderMain(object):
   def __init__(self):
       self.urls = url_manager.UrlManager()
       self.downloader = html_downloader.HtmlDownloader()
       self.parser = html_parser.HtmlParser()
       self.outputer = html_outputer.HtmlOutputer()

   def craw(self,root_url):
       count = 1
       self.urls.add_new_url(root_url)
       while self.urls.has_new_url():
           #try:
               new_url = self.urls.get_new_url()
               print 'craw %d : %s' % (count,new_url)
               html_cont = self.downloader.download(new_url)
               new_urls, new_data = self.parser.parse(new_url, html_cont)
               self.urls.add_new_urls(new_urls)
               self.outputer.collect_data(new_data)
               if count == 1000:
                   break

               count = count + 1
           #except:
               #print "craw failed"

       self.outputer.output_html()

if __name__ == "__main__":
   root_url = "https://baike.baidu.com/item/Python/407313?fr=aladdin"
   obj_spider = SpiderMain()
   obj_spider.craw(root_url)

报错如下

C:\Python27\python.exe C:/Users/Administrator/PycharmProjects/baike/baike/spider_main.py

craw 1 : https://baike.baidu.com/item/Python/407313?fr=aladdin

Traceback (most recent call last):

  File "C:/Users/Administrator/PycharmProjects/baike/baike/spider_main.py", line 34, in <module>

    obj_spider.craw(root_url)

  File "C:/Users/Administrator/PycharmProjects/baike/baike/spider_main.py", line 19, in craw

    new_urls, new_data = self.parser.parse(new_url, html_cont)

TypeError: 'NoneType' object is not iterable

Process finished with exit code 1