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python beautiful soup库入门安装教程

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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" 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

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" 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>
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())
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

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> 

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