import url_manager,html_parser,html_outputer,html_downloader 

class SpiterMain():

    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_urls))

                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_date(new_data)

                if count==1000:

                    break

                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=SpiterMain()

    obj_spider.craw(root_url)

这是什么原因啊，为什么一条都爬不出来