4.1Beautiful Soup库的小测

import requests
r=requests.get('https://python123.io/ws/demo.html')
demo=r.text
print(r.text)
# <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>
from bs4 import BeautifulSoup
soup=BeautifulSoup(demo,"html.parser")#给出的解释器是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:
#    <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>


#解析成功

4.2 Beautiful Soup库的基本元素

4.2.1Beautiful Soup库的理解

在这里插入图片描述
Beautiful Soup库是解析、遍历、维护“标签树”的功能库
只要提供的文件是标签类型，Beautiful Soup库都可以对其有很好的解析
每个标签的具体格式
p标签

属性定义标签的特点，属性由键值对构成

4.2.2Beautiful Soup库的引用

from bs4 import BeautifulSoup

4.2.3 Beautiful Soup类

在这里插入图片描述
Beautiful Soup对应一个HTML/XML文档的全部内容

4.2.4Beautiful Soup类的基本元素

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
Name	标签的名字，< p >…</>的名字是‘p’，格式：< tag >.name
Attributes	标签的属性，字典形式组织，格式为：< tag>.attrs
NavigableString	标签内的非属性字符串，<>…< />中字符串，格式为：< tag>.string
Comment	标签内字符串的注释部分，一种特殊的Comment类型

from bs4 import BeautifulSoup
import requests
r=requests.get('https://python123.io/ws/demo.html')
demo=r.text
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>

print(soup.title)
#<title>This is a python demo page</title>
tag=soup.a
print(tag)
# <a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a>

print(soup.a.name)#a
print(soup.a.parent.name)#p
print(tag.attrs)#{'href': 'http://www.icourse163.org/course/BIT-268001', 'class': ['py1'], 'id': 'link1'}
print(tag.attrs['class'])#['py1']

#a标签的链接属性
print(tag.attrs['href'])
#http://www.icourse163.org/course/BIT-268001

#标签属性的类型
print(type(tag.attrs))#<class 'dict'>

#标签类型
print(type(tag))#<class 'bs4.element.Tag'>

#查看a标签
print(soup.a)
# <a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a>
#查看a标签的字符串
print(soup.a.string)#Basic Python

print(soup.p.string)#The demo python introduces several python courses.
print(type(soup.p.string))#<class 'bs4.element.NavigableString'>


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

在这里插入图片描述

4.3 基于bs4库的HTML内容遍历方法

在这里插入图片描述
换一种表示：

4.3.1标签树的下行遍历

属性	说明
.contents	子节点的列表，将< tag >所有儿子节点存入列表中（只能获取下一级儿子节点）
.children	子节点的迭代类型，与.contents类似，用于循环遍历儿子节点
.descendants	子孙节点的迭代类型，包含所有子孙结点，用于循环遍历（可以获取所有子节点）

print(soup.head)#打印head标签
print(soup.body.contents)#打印body标签的下一级标签
print(len(soup.body.contents))#打印body标签的下一级标签的个数

import requests
r=requests.get('https://python123.io/ws/demo.html')
demo=r.text
from bs4 import BeautifulSoup
soup=BeautifulSoup(demo,"html.parser")#给出的解释器是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:
#    <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.head)
#<head><title>This is a python demo page</title></head>
print(soup.head.contents)
#[<title>This is a python demo page</title>]
print(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']
print(len(soup.body.contents))#5

print(soup.body.contents[1])
#<p class="title"><b>The demo python introduces several python courses.</b></p>

遍历儿子子孙节点

#遍历儿子节点
for child in soup.body.children:
    print(child)
#遍历子孙节点
for child in soup.body.children:
    print(child)

4.3.2 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

print(soup.title.parent)
#<head><title>This is a python demo page</title></head>

print(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>


for parent in soup.a.parents:
    if parent is None:
        print(parent)
    else:
        print(parent.name)
# p
# body
# html
# [document]

4.3.3标签树的平行遍历

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
.previos_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

平行遍历发生在同一个父节点下的各节点间
在这里插入图片描述

print(soup.a.next_sibling)#平行节点的后一个兄弟标签
#and
print(soup.a.previous_sibling)#平行节点的前一个兄弟标签
#Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:


for sibling in soup.a.next_siblings:
    print(sibling)#循环遍历后续节点
# <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">Advanced Python</a>

for sibling in soup.a.previous_siblings:
    print(sibling)#循环遍历前续节点
#Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:

4.4 基于bs4库的HTML格式化和编码

如何让< HTML>内容更加友好点？？
bs4库的prettify()方法

import requests
r=requests.get('https://python123.io/ws/demo.html')
demo=r.text
from bs4 import BeautifulSoup
soup=BeautifulSoup(demo,"html.parser")#给出的解释器是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:
#    <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>