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    python beautiful soup库入门安装教程

    作者：Cachel wood 时间：2021-09-16 17:48

    目录
    • beautiful soup库的安装
    • beautiful soup库的理解
    • beautiful soup库的引用
    • BeautifulSoup类
    • 回顾demo.html
    • Tag标签
    • Tag的attrs（属性）
    • Tag的NavigableString
    • HTML基本格式
      • 标签树的下行遍历
      • 标签树的上行遍历
      • 标签的平行遍历
    • bs库的prettify()方法
      • bs4库的编码

        beautiful soup库的安装

        pip install beautifulsoup4

        beautiful soup库的理解

        beautiful soup库是解析、遍历、维护“标签树”的功能库

        beautiful soup库的引用

        from bs4 import BeautifulSoup
import bs4

        BeautifulSoup类

        BeautifulSoup对应一个HTML/XML文档的全部内容

        回顾demo.html

        import requests

r = requests.get("http://python123.io/ws/demo.html")
demo = r.text
print(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" >Basic Python</a> and <a href="http://www.icourse163.org/course/BIT-1001870001" class="py2" >Advanced Python</a>.</p>
</body></html>

        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 

        import requests
from bs4 import BeautifulSoup
r = requests.get("http://python123.io/ws/demo.html")
demo = r.text
soup = BeautifulSoup(demo,"html.parser")
print(soup.title)
tag = soup.a
print(tag)
        <title>This is a python demo page</title>
<a  href="http://www.icourse163.org/course/BIT-268001" >Basic Python</a>

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

        Tag的name

        基本元素 说明
        Name 标签的名字，

        …

        的名字是'p',格式：.name        		 

        import requests
from bs4 import BeautifulSoup
r = requests.get("http://python123.io/ws/demo.html")
demo = r.text
soup = BeautifulSoup(demo,"html.parser")
print(soup.a.name)
print(soup.a.parent.name)
print(soup.a.parent.parent.name)
        a
p   
body

        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：.attrs 

        import requests
from bs4 import BeautifulSoup
r = requests.get("http://python123.io/ws/demo.html")
demo = r.text
soup = BeautifulSoup(demo,"html.parser")
tag = soup.a
print(tag.attrs)
print(tag.attrs['class'])
print(tag.attrs['href'])
print(type(tag.attrs))
print(type(tag))
        {'href': 'http://www.icourse163.org/course/BIT-268001', 'class': ['py1'], 'id': 'link1'}
['py1']
http://www.icourse163.org/course/BIT-268001
<class 'dict'>
<class 'bs4.element.Tag'>

        Tag的NavigableString

        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：.string

        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 

        import requests
from bs4 import BeautifulSoup
newsoup = BeautifulSoup("<b><!--This is a comment--></b><p>This is not a comment</p>","html.parser")
print(newsoup.b.string)
print(type(newsoup.b.string))
print(newsoup.p.string)
print(type(newsoup.p.string))
        This is a comment
<class 'bs4.element.Comment'>
This is not a comment
<class 'bs4.element.NavigableString'>

        HTML基本格式

        标签树的下行遍历

        属性 说明
        .contents 子节点的列表，将所有儿子结点存入列表
        .children 子节点的迭代类型，与.contents类似，用于循环遍历儿子结点
        .descendents 子孙节点的迭代类型，包含所有子孙节点，用于循环遍历

        BeautifulSoup类型是标签树的根节点

        import requests
from bs4 import BeautifulSoup
r = requests.get("http://python123.io/ws/demo.html")
demo = r.text

soup = BeautifulSoup(demo,"html.parser")
print(soup.head)
print(soup.head.contents)
print(soup.body.contents)
print(len(soup.body.contents))
print(soup.body.contents[1])
        <head><title>This is a python demo page</title></head>
[<title>This is a python demo page</title>]
['\n', <p ><b>The demo python introduces several python courses.</b></p>, '\n', <p >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" >Basic Python</a> and <a  href="http://www.icourse163.org/course/BIT-1001870001" >Advanced Python</a>.</p>, '\n']
5
<p ><b>The demo python introduces several python courses.</b></p>
        for child in soup.body.children:
	print(child)  #遍历儿子结点
for child in soup.body.descendants:
	print(child) #遍历子孙节点

        标签树的上行遍历

        属性 说明
        .parent 节点的父亲标签
        .parents 节点先辈标签的迭代类型，用于循环遍历先辈节点 

        import requests
from bs4 import BeautifulSoup
r = requests.get("http://python123.io/ws/demo.html")
demo = r.text

soup = BeautifulSoup(demo,"html.parser")
print(soup.title.parent)
print(soup.html.parent)
        <head><title>This is a python demo page</title></head>
<html><head><title>This is a python demo page</title></head>
<body>
<p ><b>The demo python introduces several python courses.</b></p>
<p >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" >Basic Python</a> and <a  href="http://www.icourse163.org/course/BIT-1001870001" >Advanced Python</a>.</p>
</body></html>
        import requests
from bs4 import BeautifulSoup
r = requests.get("http://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)
        p
body      
html      
[document]

        标签的平行遍历

        属性 说明
        .next_sibling 返回按照HTML文本顺序的下一个平行节点标签
        .previous.sibling 返回按照HTML文本顺序的上一个平行节点标签
        .next_siblings 迭代类型，返回按照HTML文本顺序的后续所有平行节点标签
        .previous.siblings 迭代类型，返回按照HTML文本顺序的前续所有平行节点标签 
        import requests
from bs4 import BeautifulSoup
r = requests.get("http://python123.io/ws/demo.html")
demo = r.text

soup = BeautifulSoup(demo,"html.parser")
print(soup.a.next_sibling)
print(soup.a.next_sibling.next_sibling)

print(soup.a.previous_sibling)
print(soup.a.previous_sibling.previous_sibling)

print(soup.a.parent)
        and 
<a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" >Advanced Python</a>
Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:

None
<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" >Basic Python</a> and <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" >Advanced Python</a>.</p>
        for sibling in soup.a.next_sibling:
	print(sibling)  #遍历后续节点
for sibling in soup.a.previous_sibling:
	print(sibling)  #遍历前续节点

        在这里插入图片描述

        bs库的prettify()方法

        import requests
from bs4 import BeautifulSoup
r = requests.get("http://python123.io/ws/demo.html")
demo = r.text

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:
    Basic Python
   </a>
   and
   <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" >
    Advanced Python
   </a>
   .
  </p>
 </body>
</html>

        .prettify()为HTML文本<>及其内容增加更加'\n'
        .prettify()可用于标签，方法：.prettify()

        bs4库的编码

        bs4库将任何HTML输入都变成utf-8编码
        python 3.x默认支持编码是utf-8,解析无障碍

        import requests
from bs4 import BeautifulSoup

soup = BeautifulSoup("<p>中文</p>","html.parser")
print(soup.p.string)

print(soup.p.prettify())
        中文

<p>  
 中文
</p>
        jsjbwy
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