XPath

XPath (XML Path Language) is a query language used to navigate and extract data from XML documents. It allows developers to select elements, attributes, and values within an XML structure using path expressions.

Example XML:

<books>
    <book>
        <title>Learning XPath</title>
        <author>John Doe</author>
        <price>29.99</price>
    </book>
    <book>
        <title>Mastering XML</title>
        <author>Jane Smith</author>
        <price>39.99</price>
    </book>
</books>

Example XPath Query:

(: Find all book titles :)
/books/book/title

Result

<title>Learning XPath</title>
<title>Mastering XML</title>

Why Use It?

• Extract specific data from XML documents.
• Navigate XML trees efficiently.
• Used in XSLT, XQuery, and Selenium for web automation.
• Supports complex queries with conditions and functions.

Syntax & Expressions

Basic Syntax

Expression	Description	Example
/	Root node	/books
//	Selects nodes anywhere	//title (all titles)
.	Current node	. (self-reference)
..	Parent node	../author (parent’s author)
@	Attribute selection	//@id (all id attributes)

Predicates (Conditions in [])

Expression	Description	Example
[index]	Selects element by index (1-based)	/books/book[1] (first book)
[text()]	Filters by text content	//book[title='Learning XPath']
[@attr]	Filters by attribute	//book[@price='29.99']

Advanced XPath Functions

String and Math functions

Function	Description	Example
contains()	Checks if a string contains a substring	//book[contains(title, 'XML')]
starts-with()	Checks string prefix	//book[starts-with(title, 'Learning')]
normalize-space()	Removes extra spaces	normalize-space(//title)
sum()	Sums numeric values	sum(//book/price)
count()	Counts nodes	count(//book)

Logical Operators

Operator	Description	Example
and	Both conditions must be true	//book[price>30 and price<40]
or	At least one condition must be true	//book[price=29.99 or price=39.99]

Real-World Application Examples

Web Scraping (Using Selenium in Python)

from selenium import webdriver
 
driver = webdriver.Chrome()
driver.get("https://example.com")
 
# Find element using XPath
element = driver.find_element("xpath", "//h1")
print(element.text)
 
driver.quit()

XSLT (Transforming XML with XPath)

<xsl:for-each select="//book">
    <xsl:value-of select="title"/>
</xsl:for-each>

API Responses (Parsing XML in Python)

import xml.etree.ElementTree as ET
 
xml_data = '''<books><book><title>Learning XPath</title></book></books>'''
tree = ET.fromstring(xml_data)
 
# XPath-like selection
titles = tree.findall(".//title")
for title in titles:
    print(title.text)