方法教程 | Python 网络爬虫实战：采集知乎一个话题下的全部问题

Posted 2021-04-06 爬小虫联盟

     “ 大家关心的其实不仅局限在爬取一个问题的回答，而是采集某一个话题下，全部问题的全部回答。所以这篇爬虫我会教大家，如何使用爬虫数据采集，爬取知乎中某一个话题下的全部问题。”

00 制定爬取策略

    我们任取一个话题（如：https://www.zhihu.com/topic/20192351/），进入话题的主页，如截图所示。

    事实上，知乎话题下的所有 “问题” 没有想象中那么容易爬取。

    为什么这么说呢？其实不是说知乎的反爬机制有多难搞，最大的困难在于它的数据，并不完整。

    我们发现， 网站上并没有任何关于话题下所有问题的列表数据，所有的数据都藏在了 “讨论”，“精华”，“等待回答” 三个页签。

    在等待回答页签下，是一些新发布的或者回答数较少的问题列表；在讨论和精华页签下，是一些精彩回答或者专栏文章的列表。

    那么，那些 热度高、关注多的问题列表呢？抱歉并没有。

    所以我的爬取策略是：

    1. 等待回答页签的问题列表，直接爬取问题ID，进行存储。

    2. 讨论和精华页签的回答数据，提取每条回答对应的问题 ID，然后去重存储。

01 抓取数据接口

    基本的策略制定好了，那么接下来的事儿，就是分别抓取 “讨论”，“精华”，“等待回答”，三个页签下的数据接口。

    在浏览器中按 F12 打开开发者工具，切换到 Network，过滤器选择 XHR。

    向下滑动网页滚动条，让网页加载新的数据。于是在开发者工具中，我们就抓取到了数据的接口。

    知乎并没有设置特别严格的反爬措施，所以不需要在反反爬方面做特殊处理，设置好参数，直接访问接口就可以了。

    下面简单说一下数据接口，看着很长的一大串，其实只需要关注三个地方就可以了，其他不用管。    

    1. 第一处（图中的 20192351 ）是话题的 ID，如果后续大家想爬其他话题的话，只需要更改这个参数即可。

    2. 第二处（图中的 top_activity ）表示是 “讨论”页签的数据接口，同理，“精华”页签是 essence ，“等待回答”是 top_question。

    3. 第三处（图中的 20.00000 ）是表示该请求的数据是第20条到第30条（从第20条开始的，每页10条数据），可以用它来控制页码，第一页就设置它为 0 （第0 - 9条），第二页就是 10（第10 - 19条）......以此类推

    具体分析网站和抓包过程，这里不再赘述了，感兴趣的话，可以参考我之前的爬虫文章。

    1. Python网络爬虫实战：爬取知乎话题下 18934 条回答数据

    2. Python爬虫基础：使用 Python 爬虫时经常遇到的问题合集

    3. Python 爬虫实战系列专栏

02 爬虫代码准备

    根据上述的分析，我们可以简单编写一下代码，进行爬取。

import requestsimport json
def fetchHotel(url): # 发起网络请求，获取数据 headers = { 'accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9', 'user-agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.97 Safari/537.36', }
 # 发起网络请求 r = requests.get(url,headers=headers) r.encoding = 'Unicode' return r.text
def parseJson(text): json_data = json.loads(text) lst = json_data['data'] nextUrl = json_data['paging']['next']
 if not lst: return;
 for item in lst: type = item['target']['type']
 if type == 'answer': # 回答 question = item['target']['question'] id = question['id'] title = question['title'] url = 'https://www.zhihu.com/question/' + str(id) print("问题：",id,title)
 elif type == 'article': #专栏 zhuanlan = item['target'] id = zhuanlan['id'] title = zhuanlan['title'] url = zhuanlan['url'] vote = zhuanlan['voteup_count'] cmts = zhuanlan['comment_count'] auth = zhuanlan['author']['name'] print("专栏：",id,title)
 elif type == 'question': # 问题 question = item['target'] id = question['id'] title = question['title'] url = 'https://www.zhihu.com/question/' + str(id) print("问题：",id,title)
 return nextUrl
if __name__ == '__main__': topicID = '20192351' url = 'https://www.zhihu.com/api/v4/topics/' + topicID + '/feeds/top_activity?include=data%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Danswer%29%5D.target.content%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Danswer%29%5D.target.is_normal%2Ccomment_count%2Cvoteup_count%2Ccontent%2Crelevant_info%2Cexcerpt.author.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Darticle%29%5D.target.content%2Cvoteup_count%2Ccomment_count%2Cvoting%2Cauthor.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Dpeople%29%5D.target.answer_count%2Carticles_count%2Cgender%2Cfollower_count%2Cis_followed%2Cis_following%2Cbadge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.annotation_detail%2Ccontent%2Chermes_label%2Cis_labeled%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%2Canswer_type%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.author.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.paid_info%3Bdata%5B%3F%28target.type%3Darticle%29%5D.target.annotation_detail%2Ccontent%2Chermes_label%2Cis_labeled%2Cauthor.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dquestion%29%5D.target.annotation_detail%2Ccomment_count%3B&limit=10&after_id=0' while url: text = fetchHotel(url)        url = parseJson(text)

下面是运行结果：

注：

     1.爬虫核心部分都在上面了，后面的部分是在此基础上做一些优化，如用数据库，多线程等，不关心的话跳过也没关系。

    2.上述代码为“讨论” 页签的爬虫代码，其他两个页签的数据，只需要仿照这个写就可以啦

    3.由于页签下混杂着回答，专栏文章，甚至还有广告，所以在解析函数中针对每种类型的数据做了相应的处理。

03 数据库准备

    由于数据量较大，并且需要数据去重，所以为了省事儿，我决定使用 mysql 数据库来进行数据存储。

    首先要安装 mysql 数据库，和 pymysql 库。

pip install pymysql

1. 创建数据库

    在 MySQL 数据库中创建数据库 zhuhuTopic 和数据表 questions，下面是我创建的表的结构。

2. 连接数据库

import pymysql
db = pymysql.connect(host='xxx.xxx.xxx.xxx', port=3306, user='zhihuTopic', passwd='xxxxxx', db='zhihuTopic', charset='utf8')cursor = db.cursor()

    将自己的数据库的 IP、端口，用户名、密码等参数填进去，运行即可完成数据库的连接。

3. 增删改查

    通过 pymysql 库操作数据库，实际上也是通过执行 SQL 语句。也就是说，自行构造 SQL 语句的字符串 sql，然后通过 cursor.excute(sql) 执行。

def queryDB(): # 查询数据库 try: sql = "select * from questions" cursor.execute(sql) data = cursor.fetchone() print(data) except Exception as e: print(e)

    查询数据时，执行 cursor.fetchone() 每次取一条数据，执行 cursor.fetchall() 一次性取全部数据，执行 cursor.fetchmany(n) 每次取 n 条数据。

def insertDB(id, title, url): #插入数据 try: sql = "insert into questions values (%s,'%s','%s')"%(id, title, url) cursor.execute(sql) db.commit() except Exception as e: db.rollback() print(e)

    更新数据，删除数据等操作的写法跟插入数据的写法一样，只要修改对应 sql 语句即可。

    如果数据库操作报错了。调试的话，首先把 sql 字符串打印出来，复制到 MySQL 数据库中执行看是否有误。

    大部分的情况下，都是 SQL语句有误引起。

    所以，我们可以将爬虫代码优化成如下：

import requestsimport jsonimport pymysql
db = pymysql.connect(host='xxx.xx.xx.xxx', port=3306, user='zhihuTopic', passwd='xxxxxx', db='zhihuTopic', charset='utf8')cursor = db.cursor()
def saveQuestionDB(id, title, url): #插入数据 try: sql = "insert into questions values (%s,'%s','%s')"%(id, title, url) cursor.execute(sql) db.commit() except Exception as e: db.rollback() print(e)
def saveArticleDB(id, title, vote, cmts, auth, url): #插入数据 try: sql = "insert into article values (%s,'%s',%s,%s,'%s', '%s')"%(id, title, vote, cmts, auth, url) cursor.execute(sql) db.commit() except Exception as e: db.rollback() print(e)
def fetchHotel(url): # 发起网络请求，获取数据 headers = { 'accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9', 'user-agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.97 Safari/537.36', }
 # 发起网络请求 r = requests.get(url,headers=headers) r.encoding = 'Unicode' return r.text
def parseJson(text): json_data = json.loads(text) lst = json_data['data'] nextUrl = json_data['paging']['next']
 if not lst: return;
 for item in lst: type = item['target']['type']
 if type == 'answer': # 回答 question = item['target']['question'] id = question['id'] title = question['title'] url = 'https://www.zhihu.com/question/' + str(id) print("问题：",id,title) # 保存到数据库 saveQuestionDB(id,title,url)
 elif type == 'article': #专栏 zhuanlan = item['target'] id = zhuanlan['id'] title = zhuanlan['title'] url = zhuanlan['url'] vote = zhuanlan['voteup_count'] cmts = zhuanlan['comment_count'] auth = zhuanlan['author']['name'] print("专栏：",id,title) # 保存到数据库 saveArticleDB(id, title, vote, cmts, auth, url)
 elif type == 'question': # 问题 question = item['target'] id = question['id'] title = question['title'] url = 'https://www.zhihu.com/question/' + str(id) print("问题：",id,title) # 保存到数据库 saveQuestionDB(id,title,url)
 return nextUrl
if __name__ == '__main__': topicID = '20192351' # 讨论 url = 'https://www.zhihu.com/api/v4/topics/' + topicID + '/feeds/top_activity?include=data%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Danswer%29%5D.target.content%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Danswer%29%5D.target.is_normal%2Ccomment_count%2Cvoteup_count%2Ccontent%2Crelevant_info%2Cexcerpt.author.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Darticle%29%5D.target.content%2Cvoteup_count%2Ccomment_count%2Cvoting%2Cauthor.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Dpeople%29%5D.target.answer_count%2Carticles_count%2Cgender%2Cfollower_count%2Cis_followed%2Cis_following%2Cbadge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.annotation_detail%2Ccontent%2Chermes_label%2Cis_labeled%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%2Canswer_type%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.author.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.paid_info%3Bdata%5B%3F%28target.type%3Darticle%29%5D.target.annotation_detail%2Ccontent%2Chermes_label%2Cis_labeled%2Cauthor.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dquestion%29%5D.target.annotation_detail%2Ccomment_count%3B&limit=10&after_id=0' while url: text = fetchHotel(url) url = parseJson(text)
 # 精华 url = 'https://www.zhihu.com/api/v4/topics/' + topicID + '/feeds/essence?include=data%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Danswer%29%5D.target.content%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Danswer%29%5D.target.is_normal%2Ccomment_count%2Cvoteup_count%2Ccontent%2Crelevant_info%2Cexcerpt.author.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Darticle%29%5D.target.content%2Cvoteup_count%2Ccomment_count%2Cvoting%2Cauthor.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Dpeople%29%5D.target.answer_count%2Carticles_count%2Cgender%2Cfollower_count%2Cis_followed%2Cis_following%2Cbadge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.annotation_detail%2Ccontent%2Chermes_label%2Cis_labeled%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%2Canswer_type%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.author.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.paid_info%3Bdata%5B%3F%28target.type%3Darticle%29%5D.target.annotation_detail%2Ccontent%2Chermes_label%2Cis_labeled%2Cauthor.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dquestion%29%5D.target.annotation_detail%2Ccomment_count%3B&limit=10&offset=0' while url: text = fetchHotel(url) url = parseJson(text)
 # 等待回答 url = 'https://www.zhihu.com/api/v4/topics/' + topicID + '/feeds/top_question?include=data%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Danswer%29%5D.target.content%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Danswer%29%5D.target.is_normal%2Ccomment_count%2Cvoteup_count%2Ccontent%2Crelevant_info%2Cexcerpt.author.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Darticle%29%5D.target.content%2Cvoteup_count%2Ccomment_count%2Cvoting%2Cauthor.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Dpeople%29%5D.target.answer_count%2Carticles_count%2Cgender%2Cfollower_count%2Cis_followed%2Cis_following%2Cbadge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.annotation_detail%2Ccontent%2Chermes_label%2Cis_labeled%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%2Canswer_type%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.author.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.paid_info%3Bdata%5B%3F%28target.type%3Darticle%29%5D.target.annotation_detail%2Ccontent%2Chermes_label%2Cis_labeled%2Cauthor.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dquestion%29%5D.target.annotation_detail%2Ccomment_count%3B&limit=10&offset=0' while url: text = fetchHotel(url) url = parseJson(text)

    另，“讨论”，“精华” 页签中除了问题的回答之外，还有一些专栏文章，顺手也爬了存数据库吧。下面是文章的数据表结构。

运行程序之后，数据库中确实爬取到了数据。

04 多线程准备

     前面的代码是单线程爬取。如果不考虑效率的话，大家完全可以等待一个页签中的数据爬取完成之后，继续爬取下一个页签。

    但是嘛，那样毕竟比较浪费时间。这里我打算用多线程来爬取，每一个线程爬取一个页签的数据，提高爬虫效率。 

import threading
def crawl_1(topicID): url = 'https://www.zhihu.com/api/v4/topics/' + topicID + '/feeds/top_activity?include=data%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Danswer%29%5D.target.content%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Danswer%29%5D.target.is_normal%2Ccomment_count%2Cvoteup_count%2Ccontent%2Crelevant_info%2Cexcerpt.author.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Darticle%29%5D.target.content%2Cvoteup_count%2Ccomment_count%2Cvoting%2Cauthor.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Dpeople%29%5D.target.answer_count%2Carticles_count%2Cgender%2Cfollower_count%2Cis_followed%2Cis_following%2Cbadge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.annotation_detail%2Ccontent%2Chermes_label%2Cis_labeled%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%2Canswer_type%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.author.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.paid_info%3Bdata%5B%3F%28target.type%3Darticle%29%5D.target.annotation_detail%2Ccontent%2Chermes_label%2Cis_labeled%2Cauthor.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dquestion%29%5D.target.annotation_detail%2Ccomment_count%3B&limit=10&after_id=0' while url: text = fetchHotel(url) url = parseJson(text) print("crawl_讨论")
def crawl_2(topicID): url = 'https://www.zhihu.com/api/v4/topics/' + topicID + '/feeds/essence?include=data%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Danswer%29%5D.target.content%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Danswer%29%5D.target.is_normal%2Ccomment_count%2Cvoteup_count%2Ccontent%2Crelevant_info%2Cexcerpt.author.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Darticle%29%5D.target.content%2Cvoteup_count%2Ccomment_count%2Cvoting%2Cauthor.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Dpeople%29%5D.target.answer_count%2Carticles_count%2Cgender%2Cfollower_count%2Cis_followed%2Cis_following%2Cbadge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.annotation_detail%2Ccontent%2Chermes_label%2Cis_labeled%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%2Canswer_type%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.author.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.paid_info%3Bdata%5B%3F%28target.type%3Darticle%29%5D.target.annotation_detail%2Ccontent%2Chermes_label%2Cis_labeled%2Cauthor.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dquestion%29%5D.target.annotation_detail%2Ccomment_count%3B&limit=10&offset=0' while url: text = fetchHotel(url) url = parseJson(text) print("crawl_精华")
def crawl_3(topicID): url = 'https://www.zhihu.com/api/v4/topics/' + topicID + '/feeds/top_question?include=data%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Danswer%29%5D.target.content%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Danswer%29%5D.target.is_normal%2Ccomment_count%2Cvoteup_count%2Ccontent%2Crelevant_info%2Cexcerpt.author.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Darticle%29%5D.target.content%2Cvoteup_count%2Ccomment_count%2Cvoting%2Cauthor.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Dpeople%29%5D.target.answer_count%2Carticles_count%2Cgender%2Cfollower_count%2Cis_followed%2Cis_following%2Cbadge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.annotation_detail%2Ccontent%2Chermes_label%2Cis_labeled%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%2Canswer_type%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.author.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.paid_info%3Bdata%5B%3F%28target.type%3Darticle%29%5D.target.annotation_detail%2Ccontent%2Chermes_label%2Cis_labeled%2Cauthor.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dquestion%29%5D.target.annotation_detail%2Ccomment_count%3B&limit=10&offset=0' while url: text = fetchHotel(url) url = parseJson(text) print("crawl_等待回答")

   

    我们将爬取讨论，精华，等待回答三个页签的代码，分别放到 crawl_1，crawl_2，crawl_3 这 3 个函数中。

    然后在主函数中启动 3 条线程，每条线程执行一个爬虫函数。

def main():
 topicID = '20192351' try: t1 = threading.Thread(target=crawl_1, args=(topicID,)) t2 = threading.Thread(target=crawl_2, args=(topicID,)) t3 = threading.Thread(target=crawl_3, args=(topicID,)) t1.start() t2.start() t3.start() except: print ("Error: 无法启动线程")

    

    但是使用多线程的话，要注意一件事情，就是有些操作是可以多条线程同时做的，比如说发起网络请求，解析数据等，但是有些操作同一时间只能允许一条线程使用，比如说文件读写，数据库操作等。

    所以，在数据库操作环节需要上锁，每次只放一个线程进去，避免多个线程同时操作数据库，造成错误。

lock = threading.Lock()
def saveQuestionDB(id, title, url): #插入数据 lock.acquire() try: sql = "insert into questions values (%s,'%s','%s')"%(id, title, url) cursor.execute(sql) db.commit() except Exception as e: db.rollback() print(e) lock.release()

    在数据库操作之前 lock.acquire() 上锁，操作完成之后，lock.release() 解锁。

最后，此爬虫的完整代码如下：

import requestsimport jsonimport pymysqlimport threading
lock = threading.Lock()db = pymysql.connect(host='xxx.xx.xx.xxx', port=3306, user='zhihuTopic', passwd='xxxxxx', db='zhihuTopic', charset='utf8')cursor = db.cursor()
def saveQuestionDB(id, title, url): #插入数据 lock.acquire() try: sql = "insert into questions values (%s,'%s','%s')"%(id, title, url) cursor.execute(sql) db.commit() except Exception as e: db.rollback() print(e) lock.release()
def saveArticleDB(id, title, vote, cmts, auth, url): #插入数据 lock.acquire() try: sql = "insert into article values (%s,'%s',%s,%s,'%s', '%s')"%(id, title, vote, cmts, auth, url) cursor.execute(sql) db.commit() except Exception as e: db.rollback() print(e) lock.release()
def fetchHotel(url): # 发起网络请求，获取数据 headers = { 'accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9', 'user-agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.97 Safari/537.36', }
 # 发起网络请求 r = requests.get(url,headers=headers) r.encoding = 'Unicode' return r.text
def parseJson(text): json_data = json.loads(text) lst = json_data['data'] nextUrl = json_data['paging']['next']
 if not lst: return;
 for item in lst: type = item['target']['type']
 if type == 'answer': # 回答 question = item['target']['question'] id = question['id'] title = question['title'] url = 'https://www.zhihu.com/question/' + str(id) print("问题：",id,title) # 保存到数据库 saveQuestionDB(id,title,url)
 elif type == 'article': #专栏 zhuanlan = item['target'] id = zhuanlan['id'] title = zhuanlan['title'] url = zhuanlan['url'] vote = zhuanlan['voteup_count'] cmts = zhuanlan['comment_count'] auth = zhuanlan['author']['name'] print("专栏：",id,title) # 保存到数据库 saveArticleDB(id, title, vote, cmts, auth, url)
 elif type == 'question': # 问题 question = item['target'] id = question['id'] title = question['title'] url = 'https://www.zhihu.com/question/' + str(id) print("问题：",id,title) # 保存到数据库 saveQuestionDB(id,title,url) return nextUrl
def crawl_1(topicID): url = 'https://www.zhihu.com/api/v4/topics/' + topicID + '/feeds/top_activity?include=data%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Danswer%29%5D.target.content%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Danswer%29%5D.target.is_normal%2Ccomment_count%2Cvoteup_count%2Ccontent%2Crelevant_info%2Cexcerpt.author.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Darticle%29%5D.target.content%2Cvoteup_count%2Ccomment_count%2Cvoting%2Cauthor.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Dpeople%29%5D.target.answer_count%2Carticles_count%2Cgender%2Cfollower_count%2Cis_followed%2Cis_following%2Cbadge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.annotation_detail%2Ccontent%2Chermes_label%2Cis_labeled%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%2Canswer_type%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.author.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.paid_info%3Bdata%5B%3F%28target.type%3Darticle%29%5D.target.annotation_detail%2Ccontent%2Chermes_label%2Cis_labeled%2Cauthor.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dquestion%29%5D.target.annotation_detail%2Ccomment_count%3B&limit=10&after_id=0' while url: text = fetchHotel(url) url = parseJson(text) print("crawl_1")
def crawl_2(topicID): url = 'https://www.zhihu.com/api/v4/topics/' + topicID + '/feeds/essence?include=data%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Danswer%29%5D.target.content%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Danswer%29%5D.target.is_normal%2Ccomment_count%2Cvoteup_count%2Ccontent%2Crelevant_info%2Cexcerpt.author.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Darticle%29%5D.target.content%2Cvoteup_count%2Ccomment_count%2Cvoting%2Cauthor.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Dpeople%29%5D.target.answer_count%2Carticles_count%2Cgender%2Cfollower_count%2Cis_followed%2Cis_following%2Cbadge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.annotation_detail%2Ccontent%2Chermes_label%2Cis_labeled%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%2Canswer_type%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.author.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.paid_info%3Bdata%5B%3F%28target.type%3Darticle%29%5D.target.annotation_detail%2Ccontent%2Chermes_label%2Cis_labeled%2Cauthor.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dquestion%29%5D.target.annotation_detail%2Ccomment_count%3B&limit=10&offset=0' while url: text = fetchHotel(url) url = parseJson(text) print("crawl_2")
def crawl_3(topicID): url = 'https://www.zhihu.com/api/v4/topics/' + topicID + '/feeds/top_question?include=data%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Danswer%29%5D.target.content%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Danswer%29%5D.target.is_normal%2Ccomment_count%2Cvoteup_count%2Ccontent%2Crelevant_info%2Cexcerpt.author.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Darticle%29%5D.target.content%2Cvoteup_count%2Ccomment_count%2Cvoting%2Cauthor.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dtopic_sticky_module%29%5D.target.data%5B%3F%28target.type%3Dpeople%29%5D.target.answer_count%2Carticles_count%2Cgender%2Cfollower_count%2Cis_followed%2Cis_following%2Cbadge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.annotation_detail%2Ccontent%2Chermes_label%2Cis_labeled%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%2Canswer_type%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.author.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Danswer%29%5D.target.paid_info%3Bdata%5B%3F%28target.type%3Darticle%29%5D.target.annotation_detail%2Ccontent%2Chermes_label%2Cis_labeled%2Cauthor.badge%5B%3F%28type%3Dbest_answerer%29%5D.topics%3Bdata%5B%3F%28target.type%3Dquestion%29%5D.target.annotation_detail%2Ccomment_count%3B&limit=10&offset=0' while url: text = fetchHotel(url) url = parseJson(text) print("crawl_3")
if __name__ == '__main__': topicID = '20192351' try: t1 = threading.Thread(target=crawl_1, args=(topicID,)) t2 = threading.Thread(target=crawl_2, args=(topicID,)) t3 = threading.Thread(target=crawl_3, args=(topicID,)) t1.start() t2.start() t3.start() except: print ("Error: 无法启动线程")

05 后记

    之前的爬虫里我基本很少使用数据库，也很少使用多线程。

    不使用数据库，一是因为爬取的数据量较小，保存到本地使用 excel 处理可能更方便；二是作为面向新手的实战教程，使用数据库会增加额外的学习成本（需要安装软件 MySQL，安装额外的库 pymysql，学习额外的语言 SQL）。

    不使用多线程，一是没必要，因为数据量太小了；二是减少对方网站服务器的访问压力；三是减少新手学习难度。

    但是说实话，在数据量大一些的情况下，使用数据库和多线程的优势立马出来了，数据的存取，爬取的效率等方面都很强悍。

    爬取完成之后，总计获取到了 17375 条问题，403 篇专栏文章，共计 17375 条数据。

    这是保存下来的Python 网络爬虫实战：爬取知乎一个话题下的全部问题，如有不足之处或更多技巧，欢迎指教补充。愿本文的分享对您之后爬虫有所帮助。谢谢～

                                                                                                   

编辑排版：筱筱 原创：机灵鹤