BeautifulSoup库的安装及测试

BeautifulSoup库解释

BeautifulSoup模块是用来从HTML/XML等文件提取所需数据的Python库.，专为快速周转项目而设计，如屏幕抓取。三个功能使其功能强大：

（1）Beautiful Soup提供了一些简单的方法和Pythonic习语，用于导航，搜索和修改解析树：用于剖析文档和提取所需内容的工具包。编写应用程序不需要太多代码
（2）Beautiful Soup会自动将传入的文档转换为Unicode，将传出的文档转换为UTF-8。你不必考虑编码，除非文档未指定编码且Beautiful Soup无法检测到编码。然后你只需要指定原始编码。
（3）Beautiful Soup位于流行的Python解析器之上，如lxml和html5lib，允许尝试不同的解析策略或交易速度以获得灵活性。

1、安装beautifulsoup库

以管理员权限运行pip install beautifulsoup4
BeautifulSoup库的安装及测试

2、测试安装结果

>>> import requests
>>> r=requests.get("http://python123.io/ws/demo.html")
>>> r.text
'<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>'
>>> demo =r.text
>>> from bs4 import BeautifulSoup                  #bs4是beautifulsoup4库的简写，这里是在bs4 库里面导入一个BeautifulSoup类
>>> soup=BeautifulSoup(demo,"html.parser")            #html.parser解析器用于解析demo的html代码
>>> 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>
>>>