一、Beautiful Soup 库的安装
Win平台：“以管理员身份运行” cmd
执行 pip install beautifulsoup4
安装小测：from bs4 import BeautifulSoup
soup=BeautifulSoup(‘<p>data</p>‘,‘html.parser‘)
print(soup.prettify())
二、Beautiful Soup 库的基本元素
1、BeautifulSoup类
from bs4 import BeautifulSoup
soup2=BeautifulSoup(open("D://demo.html"),"html.parser")
soup=BeautifulSoup("<html>data</html>","html.parser")
2、BeautifulSoup类的基本元素 <p class="title">...</p>
| 基本元素 | 说明 |
| Tag | 标签，最基本的信息组织单元，分别用<>和</>表明开头和结尾 |
| Name | 标签的名字，<p>...</p>的名字是‘p‘，格式：<tag>.name |
| Attributes | 标签的属性，字典形式组织，格式：<tag>.attrs |
| NavigableString | 标签内非属性字符串，<>...</>中字符串，格式：<tag>.string |
| Comment | 标签内字符串的注释部分，一种特殊的Comment类型 |
回顾demo.html
>>> import requests
>>> r=requests.get("http://python123.io/ws/demo.html")
>>> demo=r.text
>>> demo
‘<html><head><title>This is a python demo page</title></head>\r\n<body>\r\n<p class="title"><b>The demo python introduces several python courses.</b></p>\r\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:\r\n<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>\r\n</body></html>‘
Tag标签：任何存在于HTML语法中的标签都可以用soup.<tag>访问获得
当HTML文档中存在多个相同<tag>对应内容时，soup.<tag>返回第一个
>>> from bs4 import BeautifulSoup
>>> soup=BeautifulSoup(demo,"html.parser")
>>> soup.title
<title>This is a python demo page</title>
>>> soup.p
<p class="title"><b>The demo python introduces several python courses.</b></p>
>>> soup.a
<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a>
