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二、网络爬虫之提取（1）

程序员文章站 2022-04-16 08:20:31
Beautiful Soup库入门...

Beautiful Soup库入门

1.Beautiful Soup库的安装

pip install beautifulsop4

测试

>>> 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>'
>>> demo = r.text #demo将在后面使用
>>> from bs4 import BeautifulSoup
>>> soup =BeautifulSoup(demo,'html.parser')
>>> print(soup)
<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>
>>>

主要代码：

form bs4 import BeautifulSoup
soup = BeautifulSoup('<p>data</p>','html.parser')

2.Beautiful Soup库的基本元素

二、网络爬虫之提取（1）

3.Beautiful Soup库的引用

from bs4 import BeautifulSoup

Beautiful Soup库，也叫beautifulsoup4或 bs4约定引用方式如下，即主要是用BeautifulSoup类

import bs4

4.BeautifulSoup类

二、网络爬虫之提取（1）

5.Beautiful Soup库解析器

soup = BeautifulSoup('<html>data</html>'，'html.parser')

二、网络爬虫之提取（1）

6.BeautifulSoup类的基本元素

<p class=“title”>… </p>

二、网络爬虫之提取（1）

Tag 标签

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）

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'
>>>

Tag的attrs（属性）

>>> tag = soup.a
>>> tag.attrs
{'href': 'http://www.icourse163.org/course/BIT-268001', 'class': ['py1'], 'id': 'link1'}
>>> tag.attrs['class']
['py1']
>>> tag.attrs['href']
'http://www.icourse163.org/course/BIT-268001'
>>> type(tag.attrs)
<class 'dict'>
>>> type(tag)
<class 'bs4.element.Tag'>
>>>

一个<tag>可以有0或多个属性，字典类型

Tag的NavigableString

NavigableString 标签内非属性字符串，<>…</>中字符串，格式：<tag>.string

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

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 a comment</p>','html.parser')
>>> newsoup.b.string
'this is a comment'
>>> type(newsoup.b.string)
<class 'bs4.element.Comment'>
>>> newsoup.p.string
'this is a comment'
>>> type(newsoup.p.string)
<class 'bs4.element.NavigableString'>
>>>

7.基于bs4库的HTML内容遍历方法

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

HTML基本格式

<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>

二、网络爬虫之提取（1）

标签树的下行遍历

二、网络爬虫之提取（1）

>>> soup = BeautifulSoup(demo,'html.parser')
>>> soup.head
<head><title>This is a python demo page</title></head>
>>> soup.head.contents
[<title>This is a python demo page</title>]
>>> 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.contents)
5
>>> soup.body.contents[1]
<p class="title"><b>The demo python introduces several python courses.</b></p>
>>>

遍历儿子节点：

>>> for child in soup.body.children:
	print(child)

b遍历子孙节点：

for child in soup.body.descendants:
	print(child)

标签树的上行遍历

二、网络爬虫之提取（1）

>>> 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>
>>> soup.parent
>>> 

>>> soup = BeautifulSoup(demo,'html.parser')
>>> for parent in soup.a.parents:
	if parent is None:
		print(parent)
	else:
		print(parent.name)

p
body
html
[document]

标签树的平行遍历

二、网络爬虫之提取（1）
二、网络爬虫之提取（1）

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

遍历后序节点

for sibling in soup.a.next_sibling:
	print(sibling)

遍历前续节点

for sibling in soup.a.previous_sibling:
	print(sibling)

总结

二、网络爬虫之提取（1）

8.基于bs4库的HTML格式输出

能否让HTML内容更加“友好”的显示？

bs4库的prettify()方法

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

>>>

bs4库的编码

python3默认utf-8：

>>> soup1 =BeautifulSoup('<p>中文</p>','html.parser')
>>> soup1.p.string
'中文'
>>> print(soup1.p.prettify())
<p>
 中文
</p>
>>>

本文地址：https://blog.csdn.net/HolllllldOn/article/details/107361170

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