XML Processing in Python: Full Guide from Std Lib to lxml

1 1. Introduction
2 2. Introduction to Python libraries for handling XML
- 2.1 2.1 Standard Library: xml.etree.ElementTree
- 2.2 2.2 External Library: lxml
3 3. Parsing and Manipulating XML
- 3.1 3.1 Basic Parsing Steps
- 3.2 3.2 Searching Elements and Manipulating Attributes
4 4. Editing and Saving XML
- 4.1 4.1 How to Edit Elements
- 4.2 4.2 Writing to an XML File
5 5. Advanced Processing with External Libraries
- 5.1 5.1 Advanced XML Manipulation Using lxml
- 5.2 5.2 Converting XML with XSLT
6 6. Practice: Sample Code and Explanation
- 6.1 6.1 Example of Extracting Data from XML
- 6.2 6.2 Example of Editing and Saving XML
7 7. Summary

1. Introduction

Python is a flexible programming language that can easily handle various data formats. Among them, XML (Extensible Markup Language) is commonly used for exchanging and storing structured data, and is widely employed in API responses and configuration files. In Python, you can easily work with XML using the standard library or third‑party libraries. This article clearly explains everything from basic to advanced XML operations using Python.

2. Introduction to Python libraries for handling XML

2.1 Standard Library: xml.etree.ElementTree

Python’s standard library xml.etree.ElementTree is a convenient tool that makes it easy to read and write XML files, as well as explore and edit tree structures.

Basic parsing: import xml.etree.ElementTree as ET tree = ET.parse('data.xml') root = tree.getroot() print(root.tag) # Output: "data"In this code, the XML file named data.xml is read, and the tag of the root element is displayed. You can confirm that the output result is "data".
Error handling when the file does not exist: If the file does not exist, a FileNotFoundError will occur, so you can add exception handling as follows: try: tree = ET.parse('data.xml') root = tree.getroot() except FileNotFoundError: print("File not found.")

2.2 External Library: lxml

For advanced XML operations, the lxml library is recommended. lxml supports powerful XML processing with XPath and XSLT, making it easy to perform tasks that are difficult to achieve with the standard library.

Retrieving elements using XPath: from lxml import etree tree = etree.parse('data.xml') countries = tree.xpath('//country[@name="Liechtenstein"]') print(countries[0].tag) # Output: "country"
In this code, the country element with the attribute name=”Liechtenstein” is retrieved.

3. Parsing and Manipulating XML

3.1 Basic Parsing Steps

To parse an XML file and work with its tree structure, use xml.etree.ElementTree‘s parse(). This method reads the XML file and retrieves the tree’s root element.

Parsing from a file: import xml.etree.ElementTree as ET tree = ET.parse('example.xml') root = tree.getroot() print(root.tag) # Output: "rootTag" In this code, it reads the XML file example.xml and displays the tag name of the root element.

3.2 Searching Elements and Manipulating Attributes

To search XML elements, use find() or findall(). This allows you to easily retrieve specific elements or attributes.

Searching for elements and retrieving attributes: country = root.find('country') print(country.get('name')) # Output: "Liechtenstein"
Manipulating attributes: To manipulate an XML element’s attributes, retrieve them with get() and set them with set(). country.set('currency', 'CHF') print(country.attrib) # Output: {'name': 'Liechtenstein', 'currency': 'CHF'}

4. Editing and Saving XML

4.1 How to Edit Elements

You can edit the contents of an XML file by modifying the text or attributes of XML elements. For example, to change the text of an element, you can do the following:

Edit Element Text: rank = root.find('.rank') rank.text = '2' print(rank.text) # Output: "2"

4.2 Writing to an XML File

To save the modified XML to a file, use the write() method.

Save XML: tree.write('updated_data.xml')

5. Advanced Processing with External Libraries

5.1 Advanced XML Manipulation Using lxml

lxmlUsing the library, you can perform complex searches with XPath and convert XML to other formats using XSLT.

Searching for Elements with XPath: from lxml import etree tree = etree.parse('data.xml') countries = tree.xpath('//country') for country in countries: print(country.get('name'))

5.2 Converting XML with XSLT

Here’s an example of converting XML to HTML using XSLT.

XML to HTML Conversion: from lxml import etree xml_tree = etree.parse('data.xml') xsl_tree = etree.parse('style.xsl') transform = etree.XSLT(xsl_tree) result_tree = transform(xml_tree) result_tree.write('output.html', pretty_print=True)

6. Practice: Sample Code and Explanation

6.1 Example of Extracting Data from XML

This is a sample code that extracts data from an XML file and displays specific information.

Sample Code: import xml.etree.ElementTree as ET tree = ET.parse('data.xml') root = tree.getroot() for country in root.findall('country'): name = country.get('name') rank = country.find('rank').text print(f"Country: {name}, Rank: {rank}")

6.2 Example of Editing and Saving XML

This is a sample code that edits the values of XML elements and saves the changes.

Sample Code: import xml.etree.ElementTree as ET tree = ET.parse('data.xml') root = tree.getroot() rank = root.find('.//rank') rank.text = '2' tree.write('updated_data.xml')

7. Summary

When working with XML in Python, using the standard library xml.etree.ElementTree makes basic XML manipulation easy. Additionally, using lxml enables advanced operations such as XPath and XSLT. Refer to the code presented in the article and try manipulating XML yourself.