Python爬虫入门教程 ：知乎文章图片爬取器

版权声明：禁止转载至其它平台，转载至博客需带上此文链接。 https://blog.csdn.net/qq_41841569/article/details/86605946

1. 知乎文章图片爬取器之二博客背景

昨天写了知乎文章图片爬取器的一部分代码，针对知乎问题的答案json进行了数据抓取，博客中出现了部分写死的内容，今天把那部分信息调整完毕，并且将图片下载完善到代码中去。

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首先，需要获取任意知乎的问题，只需要你输入问题的ID，就可以获取相关的页面信息，比如最重要的合计有多少人回答问题。
问题ID为如下标红数字
https://www.zhihu.com/question/29024583

编写代码，下面的代码用来检测用户输入的是否是正确的ID，并且通过拼接URL去获取该问题下面合计有多少答案。

<span style="color:#505050"><code><span style="color:#0000ff">import</span> requests
<span style="color:#0000ff">import</span> re
<span style="color:#0000ff">import</span> pymongo
<span style="color:#0000ff">import</span> time
DATABASE_IP = <span style="color:#a31515">'127.0.0.1'</span>
DATABASE_PORT = 27017
DATABASE_NAME = <span style="color:#a31515">'sun'</span>
client = pymongo.MongoClient(DATABASE_IP,DATABASE_PORT)
db = client.sun
db.authenticate(<span style="color:#a31515">"dba"</span>, <span style="color:#a31515">"dba"</span>)
collection = db.zhihuone  <span style="color:green"># 准备插入数据</span>

BASE_URL = <span style="color:#a31515">"https://www.zhihu.com/question/{}"</span>
<span style="color:#0000ff">def</span> <span style="color:#a31515">get_totle_answers</span>(article_id):
    headers = {
        <span style="color:#a31515">"user-agent"</span>: <span style="color:#a31515">"需要自己补全 Mozilla/5.0 (Windows NT 10.0; WOW64)"</span>
    }

    <span style="color:#0000ff">with</span> requests.Session() <span style="color:#0000ff">as</span> s:
        <span style="color:#0000ff">with</span> s.get(BASE_URL.format(article_id),headers=headers,timeout=3) <span style="color:#0000ff">as</span> rep:
            html = rep.text
            pattern =re.compile( <span style="color:#a31515">'<meta itemProp="answerCount" content="(\d*?)"/>'</span>)
            s = pattern.search(html)
            print(<span style="color:#a31515">"查找到{}条数据"</span>.format(s.groups()[0]))
            <span style="color:#0000ff">return</span> s.groups()[0]

<span style="color:#0000ff">if</span> __name__ == <span style="color:#a31515">'__main__'</span>:

    <span style="color:green"># 用死循环判断用户输入的是否是数字</span>
    article_id = <span style="color:#a31515">""</span>
    <span style="color:#0000ff">while</span> <span style="color:#0000ff">not</span> article_id.isdigit():
        article_id = input(<span style="color:#a31515">"请输入文章ID："</span>)

    totle = get_totle_answers(article_id)
    <span style="color:#0000ff">if</span> int(totle)>0:
        zhi = ZhihuOne(article_id,totle)
        zhi.run()
    <span style="color:#0000ff">else</span>:
        print(<span style="color:#a31515">"没有任何数据！"</span>)
</code></span>

完善图片下载部分，图片下载地址在查阅过程中发现，存在json字段的content中，我们采用简单的正则表达式将他匹配出来。细节如下图展示

编写代码吧，下面的代码注释请仔细阅读，中间有一个小BUG，需要手动把pic3修改为pic2这个地方目前原因不明确，可能是我本地网络的原因，还有请在项目根目录先创建一个imgs的文件夹，用来存储图片

<span style="color:#505050"><code>    <span style="color:#0000ff">def</span> <span style="color:#a31515">download_img</span>(self,data):
        <span style="color:green">## 下载图片</span>
        <span style="color:#0000ff">for</span> item <span style="color:#0000ff">in</span> data[<span style="color:#a31515">"data"</span>]:
            content = item[<span style="color:#a31515">"content"</span>]
            pattern = re.compile(<span style="color:#a31515">'<noscript>(.*?)</noscript>'</span>)
            imgs = pattern.findall(content)
            <span style="color:#0000ff">if</span> len(imgs) > 0:
                <span style="color:#0000ff">for</span> img <span style="color:#0000ff">in</span> imgs:
                    match = re.search(<span style="color:#a31515">'<img src="(.*?)"'</span>, img)
                    download = match.groups()[0]
                    download = download.replace(<span style="color:#a31515">"pic3"</span>, <span style="color:#a31515">"pic2"</span>)  <span style="color:green"># 小BUG,pic3的下载不到</span>

                    print(<span style="color:#a31515">"正在下载{}"</span>.format(download), end=<span style="color:#a31515">""</span>)
                    <span style="color:#0000ff">try</span>:
                        <span style="color:#0000ff">with</span> requests.Session() <span style="color:#0000ff">as</span> s:
                            <span style="color:#0000ff">with</span> s.get(download) <span style="color:#0000ff">as</span> img_down:
                                <span style="color:green"># 获取文件名称</span>
                                file = download[download.rindex(<span style="color:#a31515">"/"</span>) + 1:]

                                content = img_down.content
                                <span style="color:#0000ff">with</span> open(<span style="color:#a31515">"imgs/{}"</span>.format(file), <span style="color:#a31515">"wb+"</span>) <span style="color:#0000ff">as</span> f:  <span style="color:green"># 这个地方进行了硬编码</span>
                                    f.write(content)

                                print(<span style="color:#a31515">"图片下载完成"</span>, end=<span style="color:#a31515">"\n"</span>)

                    <span style="color:#0000ff">except</span> Exception <span style="color:#0000ff">as</span> e:
                        print(e.args)



            <span style="color:#0000ff">else</span>:
                <span style="color:#0000ff">pass</span></code></span>

运行结果为

然后在玩知乎的过程中，发现了好多好问题