BeautifulSoup中find和find_all的使用详解

时间：2021-05-22

爬虫利器BeautifulSoup中find和find_all的使用方法

二话不说，先上段HTML例子

<html> <head> <title> index </title> </head> <body> <div> <ul> <li id="flask"class="item-0"><a href="link1.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >first item</a></li> <li class="item-1"><a href="link2.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >second item</a></li> <li class="item-inactie"><a href="link3.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" >third item</a></li> <li class="item-1"><a href="link4.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >fourth item</a></li> <li class="item-0"><a href="link5.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" >fifth item</a> </ul> </div> <li> hello world </li> </body></html>

使用BeautifulSoup前需要先构建BeautifulSoup实例

# 构建beautifulsoup实例soup = BeautifulSoup(html,'lxml')# 第一个参数是要匹配的内容# 第二个参数是beautifulsoup要采用的模块，即规则

需要注意的是，导入对的模块需要事先安装，此处导入的LXML事先已经安装。可以导入的模块可通过查询BeautifulSoup的文档查看

接下来是find和find_all的介绍

1. find
只返回第一个匹配到的对象
语法：

find(name, attrs, recursive, text, **wargs)　　　　# recursive 递归的，循环的

参数：

参数名 作用 name 查找标签 text 查找文本 attrs 基于attrs参数

例子：

# find查找一次li = soup.find('li')print('find_li:',li)print('li.text(返回标签的内容):',li.text)print('li.attrs(返回标签的属性):',li.attrs)print('li.string(返回标签内容为字符串):',li.string)

运行结果：

find_li: <li class="item-0" id="flask"><a href="link1.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >first item</a></li>
li.text(返回标签的内容): first item
li.attrs(返回标签的属性): {'id': 'flask', 'class': ['item-0']}
li.string(返回标签内容为字符串): first item

find也可以通过‘属性=值'的方法进行匹配

li = soup.find(id = 'flask')print(li,'\n')<li class="item-0" id="flask"><a href="link1.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >first item</a></li>

需要注意的是，因为class是python的保留关键字，若要匹配标签内class的属性，需要特殊的方法，有以下两种：

  • 在attrs属性用字典的方式进行参数传递
  • BeautifulSoup自带的特别关键字class_
# 第一种:在attrs属性用字典进行传递参数find_class = soup.find(attrs={'class':'item-1'})print('findclass:',find_class,'\n')# 第二种:BeautifulSoup中的特别关键字参数class_beautifulsoup_class_ = soup.find(class_ = 'item-1')print('BeautifulSoup_class_:',beautifulsoup_class_,'\n')

运行结果

findclass: <li class="item-1"><a href="link2.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >second item</a></li>

BeautifulSoup_class_: <li class="item-1"><a href="link2.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >second item</a></li>

2. find_all

返回所有匹配到的结果，区别于find（find只返回查找到的第一个结果）

语法：

find_all(name, attrs, recursive, text, limit, **kwargs)

参数名 作用 name 查找标签 text 查找文本 attrs 基于attrs参数

与find一样的语法

上代码

# find_all 查找所有li_all = soup.find_all('li')for li_all in li_all: print('---') print('匹配到的li:',li_all) print('li的内容:',li_all.text) print('li的属性:',li_all.attrs)

运行结果：

---
匹配到的li: <li class="item-0" id="flask"><a href="link1.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >first item</a></li>
li的内容: first item
li的属性: {'id': 'flask', 'class': ['item-0']}
---
匹配到的li: <li class="item-1"><a href="link2.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >second item</a></li>
li的内容: second item
li的属性: {'class': ['item-1']}
---
匹配到的li: <li cvlass="item-inactie"><a href="link3.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" >third item</a></li>
li的内容: third item
li的属性: {'cvlass': 'item-inactie'}
---
匹配到的li: <li class="item-1"><a href="link4.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >fourth item</a></li>
li的内容: fourth item
li的属性: {'class': ['item-1']}
---
匹配到的li: <li class="item-0"><a href="link5.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" >fifth item</a>
</li>
li的内容: fifth item

附上比较灵活的find_all查询方法：

# 最灵活的使用方式li_quick = soup.find_all(attrs={'class':'item-1'})for li_quick in li_quick: print('最灵活的查找方法:',li_quick)

运行结果：

  • 最灵活的查找方法: <li class="item-1"><a href="link2.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >second item</a></li>
  • 最灵活的查找方法: <li class="item-1"><a href="link4.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >fourth item</a></li>

完整代码：

# coding=utf8# @Author= CaiJunxuan# @QQ=469590490# @Wechat:15916454524# beautifulsoup# 导入beautifulsoup模块from bs4 import BeautifulSoup# HTML例子html = '''<html> <head> <title> index </title> </head> <body> <div> <ul> <li id="flask"class="item-0"><a href="link1.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >first item</a></li> <li class="item-1"><a href="link2.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >second item</a></li> <li cvlass="item-inactie"><a href="link3.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" >third item</a></li> <li class="item-1"><a href="link4.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >fourth item</a></li> <li class="item-0"><a href="link5.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" >fifth item</a> </ul> </div> <li> hello world </li> </body></html>'''# 构建beautifulsoup实例soup = BeautifulSoup(html,'lxml')# 第一个参数是要匹配的内容# 第二个参数是beautifulsoup要采用的模块,即规则# html.parser是python内置的结构匹配方法，但是效率不如lxml所以不常用# lxml 采用lxml模块# html5lib,该模块可以将内容转换成html5对象# 若想要以上功能,就需要具备对应的模块，比如使用lxml就要安装lxml# 在bs4当中有很多种匹配方法,但常用有两种:# find查找一次li = soup.find('li')print('find_li:',li)print('li.text(返回标签的内容):',li.text)print('li.attrs(返回标签的属性):',li.attrs)print('li.string(返回标签内容为字符串):',li.string)print(50*'*','\n')# find可以通过'属性 = 值'的方法进行selectli = soup.find(id = 'flask')print(li,'\n')# 因为class是python的保留关键字，所以无法直接查找class这个关键字# 有两种方法可以进行class属性查询# 第一种:在attrs属性用字典进行传递参数find_class = soup.find(attrs={'class':'item-1'})print('findclass:',find_class,'\n')# 第二种:BeautifulSoup中的特别关键字参数class_beautifulsoup_class_ = soup.find(class_ = 'item-1')print('BeautifulSoup_class_:',beautifulsoup_class_,'\n')# find_all 查找所有li_all = soup.find_all('li')for li_all in li_all: print('---') print('匹配到的li:',li_all) print('li的内容:',li_all.text) print('li的属性:',li_all.attrs)# 最灵活的使用方式li_quick = soup.find_all(attrs={'class':'item-1'})for li_quick in li_quick: print('最灵活的查找方法:',li_quick)

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