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快速上手Beautiful Soup

November 6, 2018 • Read: 868 • python

Beautiful Soup库安装

Win平台:执行pip install BeautifulSoup
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Beautiful Soup 库使用

演示HTML页面地址:https://python123.io/ws/demo.html

页面源代码

<html><head><title>This is a python demo page</title></head>
<body>
<p class="title"><b>The demo python introduces several python courses.</b></p>
<p class="course">Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
<a href="http://www.icourse163.org/course/BIT-268001" class="py1" id="link1">Basic Python</a> and <a href="http://www.icourse163.org/course/BIT-1001870001" class="py2" id="link2">Advanced Python</a>.</p>
</body></html>

手工获取demo.html源代码,浏览器右键“查看源代码”

>>> demo = '''
<html><head><title>This is a python demo page</title></head>
<body>
<p class="title"><b>The demo python introduces several python courses.</b></p>
<p class="course">Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
<a href="http://www.icourse163.org/course/BIT-268001" class="py1" id="link1">Basic Python</a> and <a href="http://www.icourse163.org/course/BIT-1001870001" class="py2" id="link2">Advanced Python</a>.</p>
</body></html>'''

或者,用Requests库获取demo.html源代码

>>> import requests
>>> r = requests.get('https://python123.io/ws/demo.html')
>>> demo = r.text

接下来使用Beautiful Soup库

>>> from bs4 from BeautifulSoup
>>> soup = BeautifulSoup(demo,'html.parser')
>>> print(soup.prettify())
<html>
 <head>
  <title>
   This is a python demo page
  </title>
 </head>
 <body>
  <p class="title">
   <b>
    The demo python introduces several python courses.
   </b>
  </p>
  <p class="course">
   Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
   <a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">
    Basic Python
   </a>
   and
   <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">
    Advanced Python
   </a>
   .
  </p>
 </body>
</html>

Beautiful Soup库的基本元素

Beautiful Soup库的理解

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Beautiful Soup库是解析、遍历、维护“标签树”的功能库
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Beautiful Soup库的引用

Beautifule Soup库,也叫BeautifulSoup4或bs4,约定引用方式如下,即主要是用BeautifulSoup类

from bs4 import BeautifulSoup
imprt bs4

BeautifulSoup类

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BeautifulSoup对应一个HTML/XML文档的全部内容

Beautiful Soup库解析器

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BeautifulSoup类的基本元素

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Tag标签
基本元素说明
Tag标签,最基本的信息组织单元,分别用<>和</>标明开头和结尾
>>> from bs4 import BeautifulSoup
>>> soup = BeautifulSoup(demo,"html.parser")
>>> soup.title
<title>This is a python demo page</title>
>>> tag = soup.a
>>> tag
<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a>

任何存在于HTML语法中的标签都可以用soup.<tag>访问获得 当HTML文档中存在多个相同<tag>对应内容时,soup.<tag>返回第一个

Tag的name(名字)
基本元素说明
Name标签的名字,<p>…</p>的名字是'p',格式:<tag>.name
>>> from bs4 import BeautifulSoup
>>> soup = BeautifulSoup(demo,"html.parser")
>>> soup.a.name
'a'
>>> soup.a.parent.name
'p'
>>> soup.a.parent.parent.name
'body'

每个<tag>都有自己的名字,通过<tag>.name获取,字符串类型

Tag的attrs(属性)
基本元素说明
Attributes标签的属性,字典形式组织,格式:<tag>.attrs
>>> soup.a.attrs
{'href': 'http://www.icourse163.org/course/BIT-268001', 'class': ['py1'], 'id': 'link1'}
>>> kv = soup.a.attrs
>>> kv['class']
['py1']
>>> kv['href']
'http://www.icourse163.org/course/BIT-268001'
>>> tyep(soup.a)
<class 'bs4.element.Tag'>
>>> type(soup.a.attrs)
<class 'dict'>

一个<tag>可以有0或多个属性,字典类型

Tag的NavigableString
基本元素说明
NavigableString标签内非属性字符串,<>…</>中字符串,格式:<tag>.string
>>> soup.a
>>> soup.a.string
'Basic Python'
>>> soup.p
<p class="title"><b>The demo python introduces several python courses.</b></p>
>>> soup.p.string
'The demo python introduces several python courses.'
>>> type(soup.p.string)
<class 'bs4.element.NavigableString'>

NavigableString可以跨越多个层次

Tag的Comment
基本元素说明
Comment标签内字符串的注释部分,一种特殊的Comment类型
>>> newsoup = BeautifulSoup("<b><!--This is a comment--></b><p>This is not a comment</p>",'html.parser')
>>> newsoup.b.string
'This is a comment'
>>> newsoup.p.string
'This is not a comment'
>>> type(newsoup.b.string)
<class 'bs4.element.Comment'>
>>> type(newsoup.p.string)
<class 'bs4.element.NavigableString'>

基于bs4库的HTMl内容遍历方法

标签树的下行遍历

>>> soup = BeautifulSoup(demo,'html.parser')
>>> soup.head
<head><title>This is a python demo page</title></head>
>>> print(soup.head.contents)
[<title>This is a python demo page</title>]
>>> print(soup.body.contents)
['\n', <p class="title"><b>The demo python introduces several python courses.</b></p>, '\n', <p class="course">Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a> and <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">Advanced Python</a>.</p>, '\n']
>>> len(soup.body.contens)
5
>>> soup.body.contens[1]
<p class="title"><b>The demo python introduces several python courses.</b></p>

标签树的迭代下行遍历

标签树的上行遍历

>>> soup = BeautifulSoup(demo,'html.parser')
>>> soup.title.parent
<head><title>This is a python demo page</title></head>
>>> soup.html.parent
<html><head><title>This is a python demo page</title></head>
<body>
<p class="title"><b>The demo python introduces several python courses.</b></p>
<p class="course">Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a> and <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">Advanced Python</a>.</p>
</body></html>

标签树的迭代上行遍历

import requests
from bs4 import BeautifulSoup
r = requests.get("https://python123.io/ws/demo.html")
demo = r.text
soup = BeautifulSoup(demo,'html.parser')
for parent in soup.a.parents:
    if parent is None:
        print(parent)
    else:
        print(parent.name)

遍历所有先辈节点,包括soup本身,所以要区别判断

标签树的平行遍历


平行遍历发生在同一个父节点下的各节点间

>>> soup = BeautifulSoup(demo,'html.parser')
>>> soup.a.next_sibling
' and '
>>> soup.a.next_sibling.next_sibling
<a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">Advanced Python</a>
>>> soup.a.previous_sibling
'Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:\r\n'

标签树的迭代平行遍历

标签树的遍历总结

bs4库的prettify()方法

prettify()方法的作用是使HTML内容更友好的展示

普通方法打印HTML文本

>>> import requests
>>> r = requests.get("https://python123.io/ws/demo.html")
>>> r.text
'<html><head><title>This is a python demo page</title></head>\r\n<body>\r\n<p class="title"><b>The demo python introduces several python courses.</b></p>\r\n<p class="course">Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:\r\n<a href="http://www.icourse163.org/course/BIT-268001" class="py1" id="link1">Basic Python</a> and <a href="http://www.icourse163.org/course/BIT-1001870001" class="py2" id="link2">Advanced Python</a>.</p>\r\n</body></html>'

使用prettify()方法

>>> from bs4 import BeautifulSoup
>>> soup = BeautifulSoup(r.text,'html.parser')
>>> soup.prettify()
'<html>\n <head>\n  <title>\n   This is a python demo page\n  </title>\n </head>\n <body>\n  <p class="title">\n   <b>\n    The demo python introduces several python courses.\n   </b>\n  </p>\n  <p class="course">\n   Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:\n   <a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">\n    Basic Python\n   </a>\n   and\n   <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">\n    Advanced Python\n   </a>\n   .\n  </p>\n </body>\n</html>'
>>> print(soup.prettify()
<html>
 <head>
  <title>
   This is a python demo page
  </title>
 </head>
 <body>
  <p class="title">
   <b>
    The demo python introduces several python courses.
   </b>
  </p>
  <p class="course">
   Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
   <a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">
    Basic Python
   </a>
   and
   <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">
    Advanced Python
   </a>
   .
  </p>
 </body>
</html>

prettify()还可用于标签,使用方法:<tag>.prettify()

>>> print(soup.a.prettify())
<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">
 Basic Python
</a>

总结

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