快速上手Beautiful Soup

Beautiful Soup 库安装展开目录

Win 平台：执行 pip install BeautifulSoup

Beautiful Soup 库使用展开目录

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 库的基本元素展开目录

Beautiful Soup 库的理解展开目录

Beautiful Soup 库是解析、遍历、维护 “标签树” 的功能库

Beautiful Soup 库的引用展开目录

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
import bs4

BeautifulSoup 类展开目录

BeautifulSoup 对应一个 HTML/XML 文档的全部内容

Beautiful Soup 库解析器展开目录

BeautifulSoup 类的基本元素展开目录

Tag 标签展开目录

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）展开目录

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）展开目录

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展开目录

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展开目录

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 内容遍历方法展开目录

标签树的下行遍历展开目录

>>> 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

标签树的上行遍历展开目录

>>> 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

标签树的平行遍历展开目录

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

标签树的遍历总结展开目录

bs4 库的 prettify () 方法展开目录

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>

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快速上手 Beautiful Soup

November 6, 2018 • Read: 4788 • python • 阅读设置