正则表达式应用的举例

小灰灰 2022-06-07 13:53 234阅读 0赞

正则表达式应用的举例

灵活使用findall与search

#coding=utf-8
    
    #导入re库文件
    import re
    
    old_url='http://www.jikexueyuan.com/course/android/?pageNum=2'
    total_page=20
    
    f=open('test.html','r')
    html=f.read()
    f.close()
    
    #爬取标题
    #在确定寻找的内容只有一个的时候，search的效率要比findall高
    title=re.search('<title>(.*?)</title>',html,re.S).group(1)
    print title
    
    #爬取链接
    links=re.findall('href="(.*?)"',html,re.S)
    for each in links:
        print each
    
    #爬取部分文字，先大再小
    text_fied=re.findall('<ul>(.*?)</ul>',html,re.S)[0]
    the_text=re.findall('">(.*?)</a>',text_fied,re.S)
    for every_text in the_text:
        print every_text
    
    #sub实现翻页
    for i in range(2,total_page+1):
        new_link=re.sub('pageNum=\d+','pageNum=%d'%i,old_url,re.S)
        print new_link

html文件:

<!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>极客学院爬虫测试</title>
    </head>
    <body>
    <div class="topic"><a href="http://jikexueyuan.com/welcom.html">欢迎参加《Python定向爬虫入门》</a>
       <div class="list">
           <ul>
               <li><a href="http://jikexueyuan.com/1.html">这是第一条</a></li>
               <li><a href="http://jikexueyuan.com/2.html">这是第二条</a></li>
               <li><a href="http://jikexueyuan.com/3.html">这是第三条</a></li>
           </ul>
       </div>
    </div>
    </body>
    </html>

输出:

极客学院爬虫测试  
http://jikexueyuan.com/welcom.html  
http://jikexueyuan.com/1.html  
http://jikexueyuan.com/2.html  
http://jikexueyuan.com/3.html  
这是第一条  
这是第二条  
这是第三条  
http://www.jikexueyuan.com/course/android/?pageNum=2  
http://www.jikexueyuan.com/course/android/?pageNum=3  
http://www.jikexueyuan.com/course/android/?pageNum=4  
http://www.jikexueyuan.com/course/android/?pageNum=5  
http://www.jikexueyuan.com/course/android/?pageNum=6  
http://www.jikexueyuan.com/course/android/?pageNum=7  
http://www.jikexueyuan.com/course/android/?pageNum=8  
http://www.jikexueyuan.com/course/android/?pageNum=9  
http://www.jikexueyuan.com/course/android/?pageNum=10  
http://www.jikexueyuan.com/course/android/?pageNum=11  
http://www.jikexueyuan.com/course/android/?pageNum=12  
http://www.jikexueyuan.com/course/android/?pageNum=13  
http://www.jikexueyuan.com/course/android/?pageNum=14  
http://www.jikexueyuan.com/course/android/?pageNum=15  
http://www.jikexueyuan.com/course/android/?pageNum=16  
http://www.jikexueyuan.com/course/android/?pageNum=17  
http://www.jikexueyuan.com/course/android/?pageNum=18  
http://www.jikexueyuan.com/course/android/?pageNum=19  
http://www.jikexueyuan.com/course/android/?pageNum=20  
  
Process finished with exit code 0