Python爬虫库BeautifulSoup的介绍与简单使用实例

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发布于 2020-03-18 10:23:35

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发布于 2020-03-18 10:23:35

BeautifulSoup是一个可以从HTML或XML文件中提取数据的Python库，本文为大家介绍下Python爬虫库BeautifulSoup的介绍与简单使用实例其中包括了，BeautifulSoup解析HTML，BeautifulSoup获取内容，BeautifulSoup节点操作，BeautifulSoup获取CSS属性等实例

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。

二、快速开始

给定html文档，产生BeautifulSoup对象

from bs4 import BeautifulSoup
html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
<p class="title"><b>The Dormouse's story</b></p>
 
<p class="story">Once upon a time there were three little sisters; and their names were
<a href="http://example.com/elsie" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="sister" id="link1">Elsie</a>,
<a href="http://example.com/lacie" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="sister" id="link2">Lacie</a> and
<a href="http://example.com/tillie" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="sister" id="link3">Tillie</a>;
and they lived at the bottom of a well.</p>
 
<p class="story">...</p>
"""
soup = BeautifulSoup(html_doc,'lxml')

输出完整文本

print(soup.prettify())

<html>
 <head>
 <title>
  The Dormouse's story
 </title>
 </head>
 <body>
 <p class="title">
  <b>
  The Dormouse's story
  </b>
 </p>
 <p class="story">
  Once upon a time there were three little sisters; and their names were
  <a class="sister" href="http://example.com/elsie" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" id="link1">
  Elsie
  </a>
  ,
  <a class="sister" href="http://example.com/lacie" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" id="link2">
  Lacie
  </a>
  and
  <a class="sister" href="http://example.com/tillie" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" id="link3">
  Tillie
  </a>
  ;
and they lived at the bottom of a well.
 </p>
 <p class="story">
  ...
 </p>
 </body>
</html>

浏览结构化数据

print(soup.title) #<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

<title>The Dormouse's story</title>
title
The Dormouse's story
head
<p class="title"><b>The Dormouse's story</b></p>
['title']
<a class="sister" href="http://example.com/elsie" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" id="link1">Elsie</a>
[<a class="sister" href="http://example.com/elsie" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" id="link1">Elsie</a>, <a class="sister" href="http://example.com/lacie" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" id="link2">Lacie</a>, <a class="sister" href="http://example.com/tillie" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" id="link3">Tillie</a>]

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 = """
<html><head><title>The Dormouse's story</title></head>
<body>
<p class="title" name="dromouse"><b>The Dormouse's story</b></p>
<p class="story">Once upon a time there were three little sisters; and their names were
<a href="http://example.com/elsie" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="sister" id="link1"><!-- Elsie --></a>,
<a href="http://example.com/lacie" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="sister" id="link2">Lacie</a> and
<a href="http://example.com/tillie" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="sister" id="link3">Tillie</a>;
and they lived at the bottom of a well.</p>
<p class="story">...</p>
"""
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 = """
<html><head><title>The Dormouse's story</title></head>
<body>
<p class="title" name="dromouse"><b>The Dormouse's story</b></p>
<p class="story">Once upon a time there were three little sisters; and their names were
<a href="http://example.com/elsie" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="sister" id="link1"><!-- Elsie --></a>,
<a href="http://example.com/lacie" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="sister" id="link2">Lacie</a> and
<a href="http://example.com/tillie" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="sister" id="link3">Tillie</a>;
and they lived at the bottom of a well.</p>
<p class="story">...</p>
"""
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 = """
<html>
  <head>
    <title>The Dormouse's story</title>
  </head>
  <body>
    <p class="story">
      Once upon a time there were three little sisters; and their names were
      <a href="http://example.com/elsie" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="sister" id="link1">
        <span>Elsie</span>
      </a>
      <a href="http://example.com/lacie" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="sister" id="link2">Lacie</a> 
      and
      <a href="http://example.com/tillie" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="sister" id="link3">Tillie</a>
      and they lived at the bottom of a well.
    </p>
    <p class="story">...</p>
"""
 
 
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='''
<div class="panel">
  <div class="panel-heading">
    <h4>Hello</h4>
  </div>
  <div class="panel-body">
    <ul class="list" id="list-1">
      <li class="element">Foo</li>
      <li class="element">Bar</li>
      <li class="element">Jay</li>
    </ul>
    <ul class="list list-small" id="list-2">
      <li class="element">Foo</li>
      <li class="element">Bar</li>
    </ul>
  </div>
</div>
'''
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')
print(soup.find_all('ul'))#查找所有ul标签下的内容
print(type(soup.find_all('ul')[0]))#查看其类型

下面的例子就是查找所有ul标签下的li标签：

from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')
for ul in soup.find_all('ul'):
  print(ul.find_all('li'))

attrs（属性）

通过属性进行元素的查找

html='''
<div class="panel">
  <div class="panel-heading">
    <h4>Hello</h4>
  </div>
  <div class="panel-body">
    <ul class="list" id="list-1" name="elements">
      <li class="element">Foo</li>
      <li class="element">Bar</li>
      <li class="element">Jay</li>
    </ul>
    <ul class="list list-small" id="list-2">
      <li class="element">Foo</li>
      <li class="element">Bar</li>
    </ul>
  </div>
</div>
'''
 
 
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')
print(soup.find_all(attrs={'id': 'list-1'}))#传入的是一个字典类型，也就是想要查找的属性
print(soup.find_all(attrs={'name': 'elements'}))

查找到的是同样的内容，因为这两个属性是在同一个标签里面的。

特殊类型的参数查找

from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')
print(soup.find_all(id='list-1'))#id是个特殊的属性，可以直接使用
print(soup.find_all(class_='element')) #class是关键字所以要用class_

————————————————

text

根据文本内容来进行选择：

html='''
<div class="panel">
  <div class="panel-heading">
    <h4>Hello</h4>
  </div>
  <div class="panel-body">
    <ul class="list" id="list-1">
      <li class="element">Foo</li>
      <li class="element">Bar</li>
      <li class="element">Jay</li>
    </ul>
    <ul class="list list-small" id="list-2">
      <li class="element">Foo</li>
      <li class="element">Bar</li>
    </ul>
  </div>
</div>
'''
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')
print(soup.find_all(text='Foo'))#查找文本为Foo的内容，但是返回的不是标签
————————————————

以说这个text在做内容匹配的时候比较方便，但是在做内容查找的时候并不是太方便。

方法

find

find用法和findall一模一样，但是返回的是找到的第一个符合条件的内容输出。

ind_parents()， find_parent()

find_parents()返回所有祖先节点，find_parent()返回直接父节点。

find_next_siblings() ,find_next_sibling()

find_next_siblings()返回后面的所有兄弟节点，find_next_sibling()返回后面的第一个兄弟节点

find_previous_siblings(),find_previous_sibling()

find_previous_siblings()返回前面所有兄弟节点,find_previous_sibling()返回前面第一个兄弟节点

find_all_next(),find_next()

find_all_next()返回节点后所有符合条件的节点，find_next()返回后面第一个符合条件的节点

find_all_previous(),find_previous()

find_all_previous()返回节点前所有符合条件的节点，find_previous()返回前面第一个符合条件的节点

CSS选择器通过select()直接传入CSS选择器即可完成选择

html='''
<div class="panel">
  <div class="panel-heading">
    <h4>Hello</h4>
  </div>
  <div class="panel-body">
    <ul class="list" id="list-1">
      <li class="element">Foo</li>
      <li class="element">Bar</li>
      <li class="element">Jay</li>
    </ul>
    <ul class="list list-small" id="list-2">
      <li class="element">Foo</li>
      <li class="element">Bar</li>
    </ul>
  </div>
</div>
'''
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')
print(soup.select('.panel .panel-heading'))#.代表class，中间需要空格来分隔
print(soup.select('ul li')) #选择ul标签下面的li标签
print(soup.select('#list-2 .element')) #'#'代表id。这句的意思是查找id为"list-2"的标签下的，class=element的元素
print(type(soup.select('ul')[0]))#打印节点类型

再看看层层嵌套的选择：

from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')
for ul in soup.select('ul'):
    print(ul.select('li'))

获取属性

from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')
for ul in soup.select('ul'):
  print(ul['id'])# 用[ ]即可获取属性
  print(ul.attrs['id'])#另一种写法

获取内容

from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')
for li in soup.select('li'):
  print(li.get_text())

用get_text（）方法就能获取内容了。

总结

推荐使用lxml解析库，必要时使用html.parser

标签选择筛选功能弱但是速度快建议使用find()、find_all() 查询匹配单个结果或者多个结果

如果对CSS选择器熟悉建议使用select()

记住常用的获取属性和文本值的方法

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