def parse_question(self, response):
question_pattern = re.compile('(.*zhihu.com/question/(d+))(/|$).*')
match_object = re.match(question_pattern, response.url)
question_id = match_object.group(2)
item_loader = ItemLoader(item=ZhihuQuestionItem(), response=response)
item_loader.add_value('zhihu_id', question_id)
item_loader.add_css('title', 'h1.QuestionHeader-title::text')
item_loader.add_css('topics', '.TopicLink .Popover div::text')
item_loader.add_value('url', response.url)
item_loader.add_css('content', '.QuestionHeader-detail div div span::text')
item_loader.add_css('answer_num', '.List-headerText span::text')
item_loader.add_css('comments_num', '.QuestionHeader-Comment button::text')
item_loader.add_css('watch_user_num', '.NumberBoard-value::text')
item = item_loader.load_item()
yield item
yield scrapy.Request(self.start_answer_url.format(question_id=question_id, offset=0, limit=20),
headers=self.headers, callback=self.parse_answer)