这篇文章主要介绍Python爬虫库BeautifulSoup怎么用，文中介绍的非常详细，具有一定的参考价值，感兴趣的小伙伴们一定要看完！
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一、介绍
BeautifulSoup库是灵活又方便的网页解析库，处理高效，支持多种解析器。利用它不用编写正则表达式即可方便地实现网页信息的提取。
Python常用解析库
| 解析器 | 使用方法 | 优势 | 劣势 |
| Python标准库 | BeautifulSoup(markup, “html.parser”) | Python的内置标准库、执行速度适中 、文档容错能力强 | Python 2.7.3 or 3.2.2)前的版本中文容错能力差 |
| lxml HTML 解析器 | BeautifulSoup(markup, “lxml”) | 速度快、文档容错能力强 | 需要安装C语言库 |
| lxml XML 解析器 | BeautifulSoup(markup, “xml”) | 速度快、唯一支持XML的解析器 | 需要安装C语言库 |
| html5lib | BeautifulSoup(markup, “html5lib”) | 最好的容错性、以浏览器的方式解析文档、生成HTML5格式的文档 | 速度慢、不依赖外部扩展 |
二、快速开始
给定html文档，产生BeautifulSoup对象
from bs4 import BeautifulSoup
html_doc = """
The Dormouse's story
The Dormouse's story
Once upon a time there were three little sisters; and their names were
Elsie,
Lacie and
Tillie;
and they lived at the bottom of a well.
...
"""
soup = BeautifulSoup(html_doc,'lxml')
输出完整文本
print(soup.prettify())
The Dormouse's story
The Dormouse's story
Once upon a time there were three little sisters; and their names were
Elsie
,
Lacie
and
Tillie
;
and they lived at the bottom of a well.
...
浏览结构化数据
print(soup.title) #标签及内容
print(soup.title.name) #<title>name属性
print(soup.title.string) #<title>内的字符串
print(soup.title.parent.name) #<title>的父标签name属性(head)
print(soup.p) # 第一个<p></p>
print(soup.p['class']) #第一个<p></p>的class
print(soup.a) # 第一个<a></a>
print(soup.find_all('a')) # 所有<a></a>
print(soup.find(id="link3")) # 所有id='link3'的标签</pre><pre><title>The Dormouse's story
title
The Dormouse's story
head
The Dormouse's story
['title']
Elsie
[Elsie, Lacie, Tillie]
Tillie
找出所有标签内的链接
for link in soup.find_all('a'):
print(link.get('href'))http://example.com/elsie
http://example.com/lacie
http://example.com/tillie
获得所有文字内容
print(soup.get_text())
The Dormouse's story
The Dormouse's story
Once upon a time there were three little sisters; and their names were
Elsie,
Lacie and
Tillie;
and they lived at the bottom of a well.
...
自动补全标签并进行格式化
html = """
The Dormouse's story
The Dormouse's story
Once upon a time there were three little sisters; and their names were
,
Lacie and
Tillie;
and they lived at the bottom of a well.
...
"""
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')#传入解析器：lxml
print(soup.prettify())#格式化代码，自动补全
print(soup.title.string)#得到title标签里的内容
标签选择器
选择元素
html = """
The Dormouse's story
The Dormouse's story
Once upon a time there were three little sisters; and their names were
,
Lacie and
Tillie;
and they lived at the bottom of a well.
...
"""
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')#传入解析器：lxml
print(soup.title)#选择了title标签
print(type(soup.title))#查看类型
print(soup.head)
获取标签名称
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')#传入解析器：lxml
print(soup.title.name)
获取标签属性
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')#传入解析器：lxml
print(soup.p.attrs['name'])#获取p标签中，name这个属性的值
print(soup.p['name'])#另一种写法，比较直接
获取标签内容
print(soup.p.string)
标签嵌套选择
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')#传入解析器：lxml
print(soup.head.title.string)
子节点和子孙节点
html = """
The Dormouse's story
Once upon a time there were three little sisters; and their names were
Elsie
Lacie
and
Tillie
and they lived at the bottom of a well.
...
"""
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')#传入解析器：lxml
print(soup.p.contents)#获取指定标签的子节点，类型是list
另一个方法，child：
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')#传入解析器：lxml
print(soup.p.children)#获取指定标签的子节点的迭代器对象
for i,children in enumerate(soup.p.children):#i接受索引，children接受内容
print(i,children)
输出结果与上面的一样，多了一个索引。注意，只能用循环来迭代出子节点的信息。因为直接返回的只是一个迭代器对象。
获取子孙节点：
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')#传入解析器：lxml
print(soup.p.descendants)#获取指定标签的子孙节点的迭代器对象
for i,child in enumerate(soup.p.descendants):#i接受索引，child接受内容
print(i,child)
父节点和祖先节点
parent
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')#传入解析器：lxml
print(soup.a.parent)#获取指定标签的父节点
parents
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')#传入解析器：lxml
print(list(enumerate(soup.a.parents)))#获取指定标签的祖先节点
兄弟节点
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')#传入解析器：lxml
print(list(enumerate(soup.a.next_siblings)))#获取指定标签的后面的兄弟节点
print(list(enumerate(soup.a.previous_siblings)))#获取指定标签的前面的兄弟节点
标准选择器
find_all( name , attrs , recursive , text , **kwargs )
可根据标签名、属性、内容查找文档。
name
html='''
Hello
