本文主要是介绍python爬虫案例，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

通过request拿到网页原源代码
通过re来提取想要的有效信息

import requests
import re

请求头

headers = {
    "User-Agent": "Mozilla/5.0 (Linux; Android 8.0; Pixel 2 Build/OPD3.170816.012) AppleWebKit/537.36 (HTML, "
                  "like Gecko) Chrome/90.0.4430.93 Mobile Safari/537.36 "
}

预编译所有re表达式

 sub = re.compile(r'<li id=".*?"><i class=".*?"></i><a href="(?P<content_url>.*?)" target=".*?" title="('
                 r'?P<title>.*?)">.*?</a><span>(?P<time>.*?)</span></li>', re.S)

detail_1 = re.compile(r'<div id="vsb_content_501">(?P<detail>.*?)<div id="div_vote_id">', re.S)
detail_1 = re.compile(r'<img border="0".*"></p>(?P<detail>.*?)<div id="div_vote_id">', re.S)

爬取网页源代码

遍历389页新闻目录页

for i in range(389, 0, -1):

在所写文档中将每页区内容区分开

  news = open("科院新闻.txt", "a", encoding='utf-8')
    news.write("*"*10)
    news.write("第"+str(390-i)+"页")
    news.write("*"*10)
    news.write("\n"*2)
    news.close()

在控制台输出进度

print("第"+str(390-i)+"页新闻下载中")

获取每一页的源代码

url = "https://news.hist.edu.cn/kyyw/"+str(i)+".htm"
resp = requests.get(url, headers=headers)
content = resp.content.decode()

匹配所需内容

  result = sub.finditer(content)

调出并使用匹配到的内容

for it in result:
    title = it.group("title")
    time = it.group("time")
    half = it.group("content_url")

拼出接下来要前往的网页

whole = "https://news.hist.edu.cn/" + half

爬取新的网页的源代码

article = requests.get(whole, headers=headers)
detail_2 = article.content.decode()

匹配所需内容

result2 = detail_1.finditer(detail_2)

创建科院新闻txt文档，
a：打开一个文件用于追加

news = open("科院新闻.txt", "a", encoding='utf-8')

调出并处理匹配到的内容

   for mor in result2:
        content = mor.group("detail")

进行数据清洗

 content = content.replace('(0, 0, 0)', '')
        content = content.replace('&', '')
        content = content.replace('<', '')
        content = content.replace('>', '')
        content = content.replace('/', '')
        content = content.replace('a', '')
        content = content.replace('b', '')
        content = content.replace('c', '')
        content = content.replace('d', '')
        content = content.replace('e', '')
        content = content.replace('f', '')
        content = content.replace('g', '')
        content = content.replace('h', '')
        content = content.replace('i', '')
        content = content.replace('j', '')
        content = content.replace('k', '')
        content = content.replace('b', '')
        content = content.replace('l', '')
        content = content.replace('m', '')
        content = content.replace('n', '')
        content = content.replace('o', '')
        content = content.replace('p', '')
        content = content.replace('q', '')
        content = content.replace('r', '')
        content = content.replace('s', '')
        content = content.replace('t', '')
        content = content.replace('u', '')
        content = content.replace('v', '')
        content = content.replace('w', '')
        content = content.replace('x', '')
        content = content.replace('y', '')
        content = content.replace('z', '')
        content = content.replace('=":', '')
        content = content.replace(';-:', '')
        content = content.replace('=":', '')
        content = content.replace(': "', '')
        content = content.replace('="-', '')
        content = content.replace('="_"', '')
        content = content.replace('\r\n', '')

写入标题，内容，时间

  news.write("《")
        news.write(title)
        news.write("》")
        news.write("\n")
        news.write(content)
        news.write("\n")
        news.write(time)
        news.write("\n" * 3)

当我们写文件时，操作系统往往不会立刻把数据写入磁盘，而是放到内存缓存起来，空闲的时候再慢慢写入。
只有调用close()方法时，操作系统才保证把没有写入的数据全部写入磁盘。忘记调用close()的后果是数据可能只写了一部分到磁盘，剩下的丢失了。

 news.close()

自己看完视频敲得，有很多操作可能有些沙雕，欢迎大佬在评论区指手画脚

这篇关于python爬虫案例的文章就介绍到这儿，希望我们推荐的文章对大家有所帮助，也希望大家多多支持为之网！