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 rel="nofollow noopener noreferrer" 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 rel="nofollow noopener noreferrer" 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 rel="nofollow noopener noreferrer" href="link3.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" >third item</a></li> <li class="item-1"><a rel="nofollow noopener noreferrer" href="link4.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >fourth item</a></li> <li class="item-0"><a rel="nofollow noopener noreferrer" 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 rel="nofollow noopener noreferrer" 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 rel="nofollow noopener noreferrer" 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 rel="nofollow noopener noreferrer" 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 rel="nofollow noopener noreferrer" 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 rel="nofollow noopener noreferrer" 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 rel="nofollow noopener noreferrer" 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 rel="nofollow noopener noreferrer" 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 rel="nofollow noopener noreferrer" 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 rel="nofollow noopener noreferrer" 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 rel="nofollow noopener noreferrer" 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 rel="nofollow noopener noreferrer" 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 rel="nofollow noopener noreferrer" 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 rel="nofollow noopener noreferrer" 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 rel="nofollow noopener noreferrer" href="link3.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" >third item</a></li> <li class="item-1"><a rel="nofollow noopener noreferrer" href="link4.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >fourth item</a></li> <li class="item-0"><a rel="nofollow noopener noreferrer" 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select li = 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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