python beautiful soup库入门安装教程

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)

The demo python introduces several python courses.
Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
Basic Python and Advanced Python.

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)

Basic Python

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

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("
This is not a comment
","html.parser")
print(newsoup.b.string)
print(type(newsoup.b.string))
print(newsoup.p.string)
print(type(newsoup.p.string))

This is a comment

This is not a comment

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])

[]
['\n', 
The demo python introduces several python courses.
, '\n', 
Python 
is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the 
following courses:
Basic Python and Advanced Python.
, '\n']
5
The demo python introduces several python courses.

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)

The demo python introduces several python courses.
Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
Basic Python and Advanced Python.

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 
Advanced Python
Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:

None
Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
Basic Python and Advanced Python.

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

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())

 
  
 
 
  

   
    The demo python introduces several python courses.
   
  
  

   Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
    Basic Python
   
   and
   
    Advanced Python
   
   .
  
 

.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("
中文
","html.parser")
print(soup.p.string)

print(soup.p.prettify())

中文

  
 中文
 

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