Don't Miss Guide: Understanding the Features Supported by lxml Selectors-HTML Tutorial-php.cn

Don't Miss Guide: Understanding the Features Supported by lxml Selectors

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Release： 2024-01-13 11:40:19

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Dont Miss Guide: Understanding the Features Supported by lxml Selectors

Want to know which selectors lxml supports? A guide not to be missed!

Overview
Selectors are one of the very important features when using lxml for Python's HTML or XML parsing. Selectors allow developers to select specific elements from an HTML or XML document through CSS selectors or XPath expressions. The lxml library not only provides powerful parsing functions, but also supports a variety of selectors, allowing developers to flexibly choose the appropriate method according to their needs.

CSS Selector
First, let’s take a look at the CSS selectors supported in the lxml library. CSS selectors are a way to select elements using a syntax similar to CSS styles. Here are some commonly used CSS selector examples:

Select elements by tag name:

from lxml import etree

html = '''
<html>
  <body>
 <p>Hello, World!</p>
 <div>
   <p>lxml tutorial</p>
   <a href="https://www.example.com">example.com</a>
 </div>
  </body>
</html>
'''

tree = etree.HTML(html)
elements = tree.cssselect('p')

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In the above example, elements will contain all elements with the  tag.

Select elements by class selector:
```
elements = tree.cssselect('.example')
```
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In the above example, .example will select all classes An element named example.

Select elements by ID selector:

element = tree.cssselect('#main')
````

在上面的示例中，`#main`将选择ID为`main`的元素。

XPath选择器
lxml库还支持XPath选择器，它是一种使用路径表达式语法来选择元素的方法。以下是一些常用的XPath选择器示例：

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Select elements by tag name:
```
elements = tree.xpath('//p')
```
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 In the example above , elements will contain all  elements.
Select elements via attribute selector:
```
elements = tree.xpath('//a[@href="https://www.example.com"]')
```
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 In the above example, elements will select all elements with href The element with the <a> tag whose attribute value is https://www.example.com.
Select elements by text content:
```
element = tree.xpath('//p[contains(text(), "lxml tutorial")]')
```
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 In the above example, element will select elements containing text content as "lxml tutorial "" element of the  tag.
Select elements by hierarchy:

在上面的示例中，`elements`将选择所有在`<div>`元素下的子孙`<p>`元素。

总结

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