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python beautiful soup库入门安装教程

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beautiful soup库的安装

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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

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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

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import requests
 
r = requests.get( "http://python123.io/ws/demo.html" )
demo = r.text
print (demo)
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< 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 >

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

  。

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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)
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< 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

  。

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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)
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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

  。

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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))
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{ '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

  。

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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))
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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 。

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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 ])
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<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' ]
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<p ><b>The demo python introduces several python courses.< / b>< / p>
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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

  。

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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)
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< 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 >
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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)
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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
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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)
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and
<a class = "py2" href = "http://www.icourse163.org/course/BIT-1001870001" id = "link2" >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" id = "link1" >Basic Python< / a> and <a class = "py2" href = "http://www.icourse163.org/course/BIT-1001870001" id = "link2" >Advanced Python< / a>.< / p>
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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

python beautiful soup库入门安装教程

bs库的prettify()方法

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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())
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< 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" id = "link2" >
     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 。

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import requests
from bs4 import BeautifulSoup
 
soup = BeautifulSoup( "<p>中文</p>" , "html.parser" )
print (soup.p.string)
 
print (soup.p.prettify())
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中文
 
<p> 
  中文
< / p>

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原文链接：https://blog.csdn.net/weixin_46530492/article/details/119960182 。

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