knowledge/technology/files/XPath.md

obj	wiki
concept	https://en.wikipedia.org/wiki/XPath

XPath

XPath (XML Path Language) is a powerful query language used to navigate and select elements from XML documents. It is commonly employed in web scraping, XML processing, and testing scenarios.

XPath Syntax

XPath expressions use a path notation to identify and navigate XML elements. The basic syntax includes:

• Node Selection: / is used to select the root node. element selects all child elements of the current node with the specified name: /root/element
• Wildcards: The * symbol is used as a wildcard for any element. /root/*
• Predicates: Square brackets [] are used to specify conditions for node selection. /root/element[@attribute='value']

Absolute XPath

Absolute XPath provides the complete path from the root node to the desired element. It starts with a single forward slash /.
/html/body/div[1]/p[2]

Relative XPath

Relative XPath selects elements based on their relationship to other elements. It does not start from the root, allowing for more flexible and adaptable expressions.
//div[@class='example']/a

XPath Functions

XPath provides various functions for more complex queries. Examples include text(), contains(), and position().
//h2[contains(text(),'XPath')]

Some functions include:

• text(): The text() function is used to select the text content of an element.
• contains(element, value): The contains() function is used to check if a string contains a specific substring.
• starts-with(element, value): The starts-with() function is used to check if a string starts with a specified prefix.
• concat(elements...): The concat() function concatenates two or more strings.
• not(element): The not() function negates a given expression.
• position(): The position() function returns the position of the current node in the selection.
• last(): The last() function returns the position of the last node in the selection.