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python Beautiful Soup 面向新手解析python Beautiful Soup基本用法

夏日的向日葵 人气:0

Beautiful Soup就是Python的一个HTML或XML的解析库,可以用它来方便地从网页中提取数据。它有如下三个特点:

首先,我们要安装它:pip install bs4,然后安装 pip install beautifulsoup4.

Beautiful Soup支持的解析器

下面我们以lxml解析器为例:

from bs4 import BeautifulSoup
soup = BeautifulSoup('<p>Hello</p>', 'lxml')
print(soup.p.string)

结果:

Hello

beautiful soup美化的效果实例:

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" class="sister" id="link1"><!-- Elsie --></a>,
<a href="http://example.com/lacie" 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" 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')#调用prettify()方法。这个方法可以把要解析的字符串以标准的缩进格式输出
print(soup.prettify())
print(soup.title.string)

结果:

<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 class="sister" href="http://example.com/elsie" 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" id="link2">
  Lacie
  </a>
  and
  <a class="sister" href="http://example.com/tillie" 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>
The Dormouse's story

下面举例说明选择元素、属性、名称的方法

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" class="sister" id="link1"><!-- Elsie --></a>,
<a href="http://example.com/lacie" 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" 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')
print('输出结果为title节点加里面的文字内容:\n',soup.title)
print('输出它的类型:\n',type(soup.title))
print('输出节点的文本内容:\n',soup.title.string)
print('结果是节点加其内部的所有内容:\n',soup.head)
print('结果是第一个p节点的内容:\n',soup.p)
print('利用name属性获取节点的名称:\n',soup.title.name)
#这里需要注意的是,有的返回结果是字符串,有的返回结果是字符串组成的列表。
# 比如,name属性的值是唯一的,返回的结果就是单个字符串。
# 而对于class,一个节点元素可能有多个class,所以返回的是列表。
print('每个节点可能有多个属性,比如id和class等:\n',soup.p.attrs)
print('选择这个节点元素后,可以调用attrs获取所有属性:\n',soup.p.attrs['name'])
print('获取p标签的name属性值:\n',soup.p['name'])
print('获取p标签的class属性值:\n',soup.p['class'])
print('获取第一个p节点的文本:\n',soup.p.string)

结果:

输出结果为title节点加里面的文字内容:
<title>The Dormouse's story</title>
输出它的类型:
<class 'bs4.element.Tag'>
输出节点的文本内容:
The Dormouse's story
结果是节点加其内部的所有内容:
<head><title>The Dormouse's story</title></head>
结果是第一个p节点的内容:
<p class="title" name="dromouse"><b>The Dormouse's story</b></p>
利用name属性获取节点的名称:
title
每个节点可能有多个属性,比如id和class等:
{'class': ['title'], 'name': 'dromouse'}
选择这个节点元素后,可以调用attrs获取所有属性:
dromouse
获取p标签的name属性值:
dromouse
获取p标签的class属性值:
['title']
获取第一个p节点的文本:
The Dormouse's story

在上面的例子中,我们知道每一个返回结果都是bs4.element.Tag类型,它同样可以继续调用节点进行下一步的选择。

html = """
<html><head><title>The Dormouse's story</title></head>
<body>
"""
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')
print('获取了head节点元素,继续调用head来选取其内部的head节点元素:\n',soup.head.title)
print('继续调用输出类型:\n',type(soup.head.title))
print('继续调用输出内容:\n',soup.head.title.string)

结果:

获取了head节点元素,继续调用head来选取其内部的head节点元素:
 <title>The Dormouse's story</title>
继续调用输出类型:
 <class 'bs4.element.Tag'>
继续调用输出内容:
 The Dormouse's story

(1)find_all()

find_all,顾名思义,就是查询所有符合条件的元素。给它传入一些属性或文本,就可以得到符合条件的元素,它的功能十分强大。

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

他的用法:

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('查询所有ul节点,返回结果是列表类型,长度为2:\n',soup.find_all(name='ul'))
print('每个元素依然都是bs4.element.Tag类型:\n',type(soup.find_all(name='ul')[0]))
#将以上步骤换一种方式,遍历出来
for ul in soup.find_all(name='ul'):
  print('输出每个u1:',ul.find_all(name='li'))
#遍历两层
for ul in soup.find_all(name='ul'):
  print('输出每个u1:',ul.find_all(name='li'))
  for li in ul.find_all(name='li'):
    print('输出每个元素:',li.string)

结果:

查询所有ul节点,返回结果是列表类型,长度为2:
 [<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>]
每个元素依然都是bs4.element.Tag类型:
 <class 'bs4.element.Tag'>
输出每个u1: [<li class="element">Foo</li>, <li class="element">Bar</li>, <li class="element">Jay</li>]
输出每个u1: [<li class="element">Foo</li>, <li class="element">Bar</li>]
输出每个u1: [<li class="element">Foo</li>, <li class="element">Bar</li>, <li class="element">Jay</li>]
输出每个元素: Foo
输出每个元素: Bar
输出每个元素: Jay
输出每个u1: [<li class="element">Foo</li>, <li class="element">Bar</li>]
输出每个元素: Foo
输出每个元素: Bar

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