使用 BeautifulSoup 按 CSS 类查找标签

在本文中，我们将讨论如何使用 BeautifulSoup 通过 CSS 查找标签。我们得到一个 HTML 文档，我们需要使用 CSS 类从文档中查找和提取标签。

例子：

HTML Document:


    


    
Extract this tag



Output:
Extract this tag

所需模块：

• bs4：它是一个Python库，用于从 HTML、XML 和其他标记语言中抓取数据。
  确保您的系统上安装了 pip。
  在终端中运行以下命令来安装这个库——

pip install bs4
or
pip install beautifulsoup4

方法：

• 导入 bs4 库
• 创建 HTML 文档
• 将内容解析为 BeautifulSoup 对象
• 按 CSS 类搜索 – CSS 属性的名称“class”是Python的保留字。如果class用作关键字参数，编译器会给出语法错误。我们可以使用关键字参数class_搜索 CSS 类
  我们可以向 class_ 传递一个字符串、一个正则表达式、一个函数或 True。
• find_all()与关键字参数class_用于查找具有给定 CSS 类的所有标签
  如果我们只需要找到一个标签，则使用find()
• 打印提取的标签。

示例 1：使用 find() 方法查找标签

Python3

# Import Module
from bs4 import BeautifulSoup
 
# HTML Document
HTML_DOC = """
              
               
                   
               
               
                   
Extract this tag
               
             
            """
 
# Function to find tags
def find_tags_from_class(html):
 
    # parse html content
    soup = BeautifulSoup(html, "html.parser")
 
    # find tags by CSS class
    div = soup.find("div", class_= "ext")
 
    # Print the extracted tag
    print(div)
 
# Function Call
find_tags_from_class(HTML_DOC)

输出：

示例 2：使用 find_all() 方法查找所有标签

蟒蛇3

# Import Module
from bs4 import BeautifulSoup
 
# HTML Document
HTML_DOC = """
              
               
                   
               
               
                
                   
                    
                    
                    
                    
                    
                   
                
 This is row 1 
 This is row 2 
 This is row 3 
 This is row 4 
 This is row 5 
               
             
            """
 
# Function to find tags
def find_tags_from_class(html):
 
    # parse html content
    soup = BeautifulSoup(html, "html.parser")
 
    # find tags by CSS class
    rows = soup.find_all("td", class_= "table-row")
 
    # Print the extracted tag
    for row in rows:
        print(row)
 
# Function Call
find_tags_from_class(HTML_DOC)

输出：

示例 3：使用正则表达式按 CSS 类查找标签。

蟒蛇3

# Import Module
from bs4 import BeautifulSoup
import re
 
# HTML Document
HTML_DOC = """
              
               
                   
               
               
                
                   
                    
                    
                    
                    
                    
                   
                
 This is row 1 
 This is row 2 
 This is row 3 
 This is row 4 
 This is row 5 
               
             
            """
 
# Function to find tags
def find_tags_from_class(html):
 
    # parse html content
    soup = BeautifulSoup(html, "html.parser")
 
    # find tags by CSS class using regular expressions
    # $ is used to match pattern ending with
    # Here we are finding class that ends with "row"
    rows = soup.find_all("td", class_= re.compile("row$"))
 
    # Print the extracted tag
    for row in rows:
        print(row)
 
# Function Call
find_tags_from_class(HTML_DOC)

输出：

解释：

 This is row 2 
 This is row 4 

以上两个标签类名以“row”结尾。因此，它们被提取。其他标签类名不以“row”结尾。因此，它们不会被提取。

示例 4：使用用户定义函数按 CSS 类查找标签。

蟒蛇3

# Import Module
from bs4 import BeautifulSoup
 
# HTML Document
HTML_DOC = """
              
               
                   
               
               
                
                   
                    
                    
                    
                    
                    
                   
                
 This is invalid because len(table) != 3 
 This is valid because len(row) == 3 
 This is invalid because len(data) != 3 
 This is valid because len(hii) == 3 
 This is invalid because class is None 
               
             
            """
 
# Returns true if the css_class is not None
# and length of css_class is equal to 3
# else returns false
def has_three_characters(css_class):
    return css_class is not None and len(css_class) == 3
 
 
# Function to find tags
def find_tags_from_class(html):
 
    # parse html content
    soup = BeautifulSoup(html, "html.parser")
 
    # find tags by CSS class using user-defined function
    rows = soup.find_all("td", class_= has_three_characters)
 
    # Print the extracted tag
    for row in rows:
        print(row)
 
# Function Call
find_tags_from_class(HTML_DOC)

输出：

示例 5：从网站中按 CSS 类查找标签

蟒蛇3

# Import Module
from bs4 import BeautifulSoup
import requests
 
# Assign website
import requests
URL = "https://www.geeksforgeeks.org/"
HTML_DOC = requests.get(URL)
 
# Function to find tags
def find_tags_from_class(html):
 
    # parse html content
    soup = BeautifulSoup(html.content, "html5lib")
 
    # find tags by CSS class
    div = soup.find("div", class_= "article--container_content")
 
    # Print the extracted tag
    print(div)
 
# Function Call
find_tags_from_class(HTML_DOC)

输出：