爬虫实战系列(九)：知乎热榜全爬取及词云制作

声明：本博客只是简单的爬虫示范，并不涉及任何商业用途。

一.前言

今天正值国庆中秋双节，但作为一个技术宅的我仍然是在寝室度过，在下午我还是习惯性地打开知乎，结果发现《姜子牙》冲到了知乎热榜第一，而我最近也有意向去看这部国产动漫。于是不了解风评的我准备利用爬虫+词云图对《姜子牙》的评价进行可视化，然后决定一波到底要不要去看，顺带的我也把热榜其他问题和对应的全部回答也扒了下来，下面是热榜全爬取的详细记录。

二.爬虫过程

2.1 所有问题对应回答页面链接获取

首先，进入知乎热榜页面(展示如下图)，可以看到热榜中一共包括了50个问题，这些问题的所有回答都是我们要爬取的目标。

随机选中一个问题右键检查即可查看所有的元素都包含在一个<section>...</section>块中，即：

我们点开其中的一个元素，可以发现对应的问题及其所指向的链接，即我们需要的链接：

2.2 获取单个问题页面的全部回答

在解决了热榜所有问题的链接获取之后，下面的问题就是如何爬取单个页面的所有回答了，我们打开《姜子牙》的链接，可以看到如下页面：

需要注意的是：该页面的所有回答并不会全部显示出来，而是当滚动条滚动到底部后才会出现新的回答，即它采用了Ajax 动态加载的技术。那该问题如何解决呢，我在开发者工具中，选中请求类型为XHR，结果果然看到了评论数据(json格式)：

我又继续滚动滑动条几次，得到如下几个链接：

https://www.zhihu.com/api/v4/questions/337873977/answers?include=data%5B%2A%5D.is_normal%2Cadmin_closed_comment%2Creward_info%2Cis_collapsed%2Cannotation_action%2Cannotation_detail%2Ccollapse_reason%2Cis_sticky%2Ccollapsed_by%2Csuggest_edit%2Ccomment_count%2Ccan_comment%2Ccontent%2Ceditable_content%2Cvoteup_count%2Creshipment_settings%2Ccomment_permission%2Ccreated_time%2Cupdated_time%2Creview_info%2Crelevant_info%2Cquestion%2Cexcerpt%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%2Cis_labeled%2Cis_recognized%2Cpaid_info%2Cpaid_info_content%3Bdata%5B%2A%5D.mark_infos%5B%2A%5D.url%3Bdata%5B%2A%5D.author.follower_count%2Cbadge%5B%2A%5D.topics&limit=5&offset=5&platform=desktop&sort_by=default
https://www.zhihu.com/api/v4/questions/337873977/answers?include=data%5B%2A%5D.is_normal%2Cadmin_closed_comment%2Creward_info%2Cis_collapsed%2Cannotation_action%2Cannotation_detail%2Ccollapse_reason%2Cis_sticky%2Ccollapsed_by%2Csuggest_edit%2Ccomment_count%2Ccan_comment%2Ccontent%2Ceditable_content%2Cvoteup_count%2Creshipment_settings%2Ccomment_permission%2Ccreated_time%2Cupdated_time%2Creview_info%2Crelevant_info%2Cquestion%2Cexcerpt%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%2Cis_labeled%2Cis_recognized%2Cpaid_info%2Cpaid_info_content%3Bdata%5B%2A%5D.mark_infos%5B%2A%5D.url%3Bdata%5B%2A%5D.author.follower_count%2Cbadge%5B%2A%5D.topics&limit=5&offset=10&platform=desktop&sort_by=default
https://www.zhihu.com/api/v4/questions/337873977/answers?include=data%5B%2A%5D.is_normal%2Cadmin_closed_comment%2Creward_info%2Cis_collapsed%2Cannotation_action%2Cannotation_detail%2Ccollapse_reason%2Cis_sticky%2Ccollapsed_by%2Csuggest_edit%2Ccomment_count%2Ccan_comment%2Ccontent%2Ceditable_content%2Cvoteup_count%2Creshipment_settings%2Ccomment_permission%2Ccreated_time%2Cupdated_time%2Creview_info%2Crelevant_info%2Cquestion%2Cexcerpt%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%2Cis_labeled%2Cis_recognized%2Cpaid_info%2Cpaid_info_content%3Bdata%5B%2A%5D.mark_infos%5B%2A%5D.url%3Bdata%5B%2A%5D.author.follower_count%2Cbadge%5B%2A%5D.topics&limit=5&offset=15&platform=desktop&sort_by=default

观察上述链接我们可以看到变化的只有offset字段，而且是加5递增的，因此我们只需要改变该链接的offset字段即可获取到对应问题的全部回答所对应的链接。此外，我又打开了其他几个问题得到如下链接：

https://www.zhihu.com/api/v4/questions/337873977/answers?include=data%5B%2A%5D.is_normal%2Cadmin_closed_comment%2Creward_info%2Cis_collapsed%2Cannotation_action%2Cannotation_detail%2Ccollapse_reason%2Cis_sticky%2Ccollapsed_by%2Csuggest_edit%2Ccomment_count%2Ccan_comment%2Ccontent%2Ceditable_content%2Cvoteup_count%2Creshipment_settings%2Ccomment_permission%2Ccreated_time%2Cupdated_time%2Creview_info%2Crelevant_info%2Cquestion%2Cexcerpt%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%2Cis_labeled%2Cis_recognized%2Cpaid_info%2Cpaid_info_content%3Bdata%5B%2A%5D.mark_infos%5B%2A%5D.url%3Bdata%5B%2A%5D.author.follower_count%2Cbadge%5B%2A%5D.topics&limit=5&offset=5&platform=desktop&sort_by=default
https://www.zhihu.com/api/v4/questions/423719681/answers?include=data%5B%2A%5D.is_normal%2Cadmin_closed_comment%2Creward_info%2Cis_collapsed%2Cannotation_action%2Cannotation_detail%2Ccollapse_reason%2Cis_sticky%2Ccollapsed_by%2Csuggest_edit%2Ccomment_count%2Ccan_comment%2Ccontent%2Ceditable_content%2Cvoteup_count%2Creshipment_settings%2Ccomment_permission%2Ccreated_time%2Cupdated_time%2Creview_info%2Crelevant_info%2Cquestion%2Cexcerpt%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%2Cis_labeled%2Cis_recognized%2Cpaid_info%2Cpaid_info_content%3Bdata%5B%2A%5D.mark_infos%5B%2A%5D.url%3Bdata%5B%2A%5D.author.follower_count%2Cbadge%5B%2A%5D.topics&limit=5&offset=5&platform=desktop&sort_by=default
https://www.zhihu.com/api/v4/questions/423737325/answers?include=data%5B%2A%5D.is_normal%2Cadmin_closed_comment%2Creward_info%2Cis_collapsed%2Cannotation_action%2Cannotation_detail%2Ccollapse_reason%2Cis_sticky%2Ccollapsed_by%2Csuggest_edit%2Ccomment_count%2Ccan_comment%2Ccontent%2Ceditable_content%2Cvoteup_count%2Creshipment_settings%2Ccomment_permission%2Ccreated_time%2Cupdated_time%2Creview_info%2Crelevant_info%2Cquestion%2Cexcerpt%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%2Cis_labeled%2Cis_recognized%2Cpaid_info%2Cpaid_info_content%3Bdata%5B%2A%5D.mark_infos%5B%2A%5D.url%3Bdata%5B%2A%5D.author.follower_count%2Cbadge%5B%2A%5D.topics&limit=5&offset=5&platform=desktop&sort_by=default

观察可知，不同问题的回答对应的链接的不同之处只包括问题ID和对应各自问题的offset，因此我们只需要在进入每个问题的回答页面时，将对应的问题ID和回答数获取即可获取包含所有回答的json数据。
注：具体如何从json数据中提取作者和对应的回答的过程就不详细介绍了。

2.3 爬虫结果保存

在爬取的过程中，由于首先要获取到热榜各个问题对应的链接，因此我将各个问题及其对应的回答页面的链接保存了下来，格式为csv，其所包含的字段展示如下：

字段一	字段二
title(问题)	url (问题对应的回答页面)

另外，对于所有问题的回答都单独存为一个csv文件，每个csv文件包含的字段如下：

字段一	字段二
author(回答者)	content(回答内容，只筛选了其中的中文内容)

2.4 全过程流程总结

综上，爬虫的全过程已经一目了然了，首先是获取热榜所有问题的链接(顺便可以获取问题ID)，然后进入到具体的某个页面获取回答数，然后就可以构造链接来爬取回答了，最后将回答保存为csv格式，即：

三.示例程序及结果展示

import requests
from bs4 import BeautifulSoup
import pandas as pd
import re
import json
import tracebackchinese = '[\u4e00-\u9fa5]+' #提取中文汉字的patternheaders = {'user-agent': '换上自己的User-Agent','cookie': '换上自己的知乎登录cookie'
}def getHots(url='https://www.zhihu.com/hot'):"""功能：获取知乎热榜所有话题的id"""topics = []response = requests.get(url=url,headers=headers)if response.status_code == 200:soup = BeautifulSoup(response.content,'lxml',from_encoding='utf-8')hots = soup.findAll('section',attrs={'class':'HotItem'})for hot in hots:hot_url = hot.find('a').get('href')hot_c = hot.find('a').get('title')print(hot_c,hot_url)topics.append([hot_c,hot_url])Saver(topics,0,['title','url'])return topicsdef getNumber(topic_url):"""功能：获取某个问题的回答数"""response = requests.get(topic_url,headers=headers)if response.status_code == 200:soup = BeautifulSoup(response.content,'lxml',from_encoding='utf-8')string = soup.find('h4',attrs={'class':'List-headerText'}).get_text()number = ''.join([s for s in string if s.isdigit()])return int(number)return 0def getAnswers(question_id,number):"""功能：获取某个问题各个回答question_id：话题idnumber：回答数量"""outcome = []i = 0while i * 5 < number:try:url = 'https://www.zhihu.com/api/v4/questions/{}/answers?include=data%5B%2A%5D.is_normal%2Cadmin_closed_comment%2Creward_info%2Cis_collapsed%2Cannotation_action%2Cannotation_detail%2Ccollapse_reason%2Cis_sticky%2Ccollapsed_by%2Csuggest_edit%2Ccomment_count%2Ccan_comment%2Ccontent%2Ceditable_content%2Cvoteup_count%2Creshipment_settings%2Ccomment_permission%2Ccreated_time%2Cupdated_time%2Creview_info%2Crelevant_info%2Cquestion%2Cexcerpt%2Crelationship.is_authorized%2Cis_author%2Cvoting%2Cis_thanked%2Cis_nothelp%2Cis_labeled%2Cis_recognized%2Cpaid_info%2Cpaid_info_content%3Bdata%5B%2A%5D.mark_infos%5B%2A%5D.url%3Bdata%5B%2A%5D.author.follower_count%2Cbadge%5B%2A%5D.topics&limit=5&offset={}&platform=desktop&sort_by=default'.format(question_id,i*5)response = requests.get(url,headers=headers)if response.status_code == 200:js = json.loads(response.text)for answer in js['data']:author = answer['author']['name']content = ''.join(re.findall(chinese,answer['content']))print(author,content)outcome.append([author,content])i += 1except Exception:i += 1print(traceback.print_exc())print('web spider fails')return outcomedef Saver(datas,idx,columns):"""功能：保存数据为csv格式index：话题索引"""df = pd.DataFrame(datas,columns=columns)df.to_csv('./datas/hot_{}.csv'.format(idx),index=False)def Spider():"""功能：爬虫主函数"""topics = getHots()for idx,topic in enumerate(topics):print('clawling: {} numbers: {}'.format(topic[0],topic[1]))#获取question IDquestion_id = topic[1].split('/')[-1]#获取回答数number = getNumber(topic[1])#爬取对应问题的所有回答datas = getAnswers(question_id,number)#保存回答为.csv格式Saver(datas,idx + 1,['author','content'])if __name__ == "__main__":Spider()

最后爬取的50个问题都保存为了单独的csv文件，然后我分别对其进行了jieba分词，删除停用词，最后利用wordcloud模块都生成了各自的词云图，下面是《姜子牙》的某个问题所对应的词云图：

四.结语

完整项目和数据地址：zhihu_answer_demo
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