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python scrapy爬取知乎问题和收藏夹下所有答案的…

2018-09-18 06:43:15来源：博客园阅读 ()

上文介绍了爬取知乎问题信息的整个过程,这里介绍下爬取问题下所有答案的内容和图片,大致过程相同,部分核心代码不同.

爬取一个问题的所有内容流程大致如下:

一个问题url
请求url,获取问题下的答案个数(我不需要,因为之前获取问题信息的时候保存了问题的回答个数)
通过答案的接口去获取答案(如果一次获取5个答案,总计100个答案,需要计算的出访问20次答案接口)[答案的接口地址如下图所示]
答案接口返回的内容保存到mysql
提取内容中的图片地址,保存到本地

爬取代码:

从mysql库中查到question的id, 然后直接访问答案接口去获取数据.

answer_template="https://www.zhihu.com/api/v4/questions/%s/answers?include=data[*].is_normal,admin_closed_comment,reward_info,is_collapsed,annotation_action,annotation_detail,collapse_reason,is_sticky,collapsed_by,suggest_edit,comment_count,can_
comment,content,editable_content,voteup_count,reshipment_settings,comment_permission,created_time,updated_time,review_info,relevant_info,question,excerpt,relationship.is_authorized,is_author,voting,is_thanked,is_nothelp;data[*].mark_infos[*].url;dat
a[*].author.follower_count,badge[?(type=best_answerer)].topics&limit=5&offset=%s&sort_by=default"
    def check_login(self, response):
         #从mysql中读取question的信息,来进行爬取
         db = MySQLdb.connect("localhost", "root", "", "crawl", charset='utf8' )
         cursor = db.cursor()
         selectsql="select questionid,answer_num from  zhihu_question where id in ( 251,138,93,233,96,293,47,24,288,151,120,311,214,33) ;"
         try:
             cursor.execute(selectsql)    
             results = cursor.fetchall()
             for row in results:
                 questionid = row[0]
                 answer_num = row[1]
                 fornum = answer_num/5 #计算需要访问答案接口的次数
                 print("questionid : "+ str(questionid)+"   answer_Num: "+str(answer_num))
                 for i in range(fornum+1):
                     answer_url = self.answer_template % (str(questionid), str(i*5))
                     yield scrapy.Request(answer_url,callback=self.parse_answer, headers=self.headers) 
         except Exception as e:
             print(e)
         db.close()

解析response

parser_anser解析接口里的内容,这里就比较方便了, 因为是json格式的
代码如下:

def parse_answer(self,response):
        #测试时把返回结果写到本地, 然后写pythonmain方法测试,测试方法都在test_code目录下
        #temfn= str(random.randint(0,100))
        #f = open("/var/www/html/scrapy/answer/"+temfn,'wb')
        #f.write(response.body)
        #f.write("------")
        #f.close() 
        res=json.loads(response.text)
        #print (res)
        data=res['data']
        # 一次返回多个(默认5个)答案, 需要遍历
        for od in data:
            #print(od)
            item = AnswerItem()
            item['answer_id']=str(od['id'])  #  answer id
            item['question_id']=str(od['question']['id'])
            item['question_title']=od['question']['title']
            item['author_url_token']=od['author']['url_token']
            item['author_name']=od['author']['name']
            item['voteup_count']=str(od['voteup_count'])
            item['comment_count']=str(od["comment_count"])
            item['content']=od['content']
            yield item
            testh = etree.HTML(od['content'])
            itemimg = MyImageItem()
            itemimg['question_answer_id'] = str(od['question']['id'])+"/"+str(od['id'])
            itemimg['image_urls']=testh.xpath("//img/@data-original")
            yield itemimg