How to use the beautifulsoup module to parse web pages in Python 3.x

How to use the Beautiful Soup module in Python 3.x for web page parsing

Introduction:
When developing web pages and crawling data, it is usually necessary to capture the required data from the web page. The structure of web pages is often more complex, and using regular expressions to find and extract data can become difficult and cumbersome. At this time, Beautiful Soup becomes a very effective tool, which can help us easily parse and extract data on the web page.

1. Beautiful Soup Introduction
   Beautiful Soup is a Python third-party library used to extract data from HTML or XML files. It supports HTML parsers in the Python standard library, such as lxml, html5lib, etc.
   First, we need to use pip to install the Beautiful Soup module:

   pip install beautifulsoup4

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2. Import library
   After the installation is complete, we need to import the Beautiful Soup module to use its functions. At the same time, we also need to import the requests module to obtain web content.

   import requests
   from bs4 import BeautifulSoup

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3. Initiate HTTP request to obtain web page content

   # 请求页面
   url = 'http://www.example.com'
   response = requests.get(url)
   # 获取响应内容，并解析为文档树
   html = response.text
   soup = BeautifulSoup(html, 'lxml')

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4. Tag selector
   Before using Beautiful Soup to parse web pages, you first need to understand how Select a label. Beautiful Soup provides some simple and flexible tag selection methods.

   # 根据标签名选择
   soup.select('tagname')
   # 根据类名选择
   soup.select('.classname')
   # 根据id选择
   soup.select('#idname')
   # 层级选择器
   soup.select('father > son')

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5. Get tag content
   After we select the required tag according to the tag selector, we can use a series of methods to get the content of the tag. Here are some commonly used methods:

   # 获取标签文本
   tag.text
   # 获取标签属性值
   tag['attribute']
   # 获取所有标签内容
   tag.get_text()

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6. Full Example
   Here is a complete example that demonstrates how to use Beautiful Soup to parse a web page and get the required data.

   import requests
   from bs4 import BeautifulSoup
   
   # 请求页面
   url = 'http://www.example.com'
   response = requests.get(url)
   # 获取响应内容，并解析为文档树
   html = response.text
   soup = BeautifulSoup(html, 'lxml')
   
   # 选择所需标签
   title = soup.select('h1')[0]
   # 输出标签文本
   print(title.text)
   
   # 获取所有链接标签
   links = soup.select('a')
   # 输出链接的文本和地址
   for link in links:
    print(link.text, link['href'])

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Summary:
Through the introduction of this article, we have learned how to use the Beautiful Soup module in Python to parse web pages. We can select tags in the web page through the selector, and then use the corresponding methods to obtain the tag's content and attribute values. Beautiful Soup is a powerful and easy-to-use tool that provides a convenient way to parse web pages and greatly simplifies our development work.

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