XML

XML (eXtensible Markup Language) is a markup language for storing and transporting structured data. Python’s xml.dom.minidom module provides a lightweight DOM (Document Object Model) interface for parsing and creating XML.

XML Structure

An XML document consists of elements organised in a tree structure:

<?xml version="1.0" encoding="UTF-8"?>
<catalogue>
    <book id="1">
        <title>Python Basics</title>
        <author>Alice Smith</author>
        <price>29.99</price>
    </book>
    <book id="2">
        <title>Data Science</title>
        <author>Bob Jones</author>
        <price>39.99</price>
    </book>
</catalogue>

Key concepts:

• Element: A node defined by opening and closing tags (e.g., <title>...</title>)

• Attribute: A name-value pair within an opening tag (e.g., id="1")

• Text content: The data between opening and closing tags

Reading XML

from xml.dom.minidom import parse

# Parse an XML file
doc = parse("catalogue.xml")

# Get all book elements
books = doc.getElementsByTagName("book")

for book in books:
    # Get attribute value
    book_id = book.getAttribute("id")

    # Get text content of child elements
    title = book.getElementsByTagName("title")[0].firstChild.nodeValue
    author = book.getElementsByTagName("author")[0].firstChild.nodeValue
    price = book.getElementsByTagName("price")[0].firstChild.nodeValue

    print(f"ID: {book_id}, Title: {title}, Author: {author}, Price: {price}")

Writing XML

from xml.dom.minidom import parse

# Parse existing file
doc = parse("catalogue.xml")

# Modify an attribute
books = doc.getElementsByTagName("book")
books[0].setAttribute("id", "100")

# Modify text content
title_elem = books[0].getElementsByTagName("title")[0]
title_elem.firstChild.replaceWholeText("Advanced Python")

# Write back to file
with open("catalogue_modified.xml", "w", encoding="utf-8") as f:
    doc.writexml(f, indent="", addindent="    ", newl="\n", encoding="utf-8")

Methods Reference

Method	Description
doc.getElementsByTagName(name)	Returns a list of all elements with the given tag name
elem.getAttribute(name)	Returns the value of an attribute
elem.getAttributeNode(name)	Returns the attribute node object
elem.setAttribute(name, value)	Sets or creates an attribute
elem.firstChild.nodeValue	Gets the text content of an element
elem.firstChild.replaceWholeText(text)	Replaces the text content
elem.hasAttribute(name)	Checks if an attribute exists
elem.removeAttribute(name)	Removes an attribute

Complete Example

from xml.dom.minidom import parse

# Parse the file
doc = parse("catalogue.xml")

# Find all books
books = doc.getElementsByTagName("book")
print(f"Found {len(books)} books\n")

# Print each book's details
for book in books:
    book_id = book.getAttribute("id")
    title = book.getElementsByTagName("title")[0].firstChild.nodeValue
    author = book.getElementsByTagName("author")[0].firstChild.nodeValue
    price = float(book.getElementsByTagName("price")[0].firstChild.nodeValue)
    print(f"[{book_id}] {title} by {author} — ${price:.2f}")

# Find a specific book by attribute
for book in books:
    if book.getAttribute("id") == "2":
        title = book.getElementsByTagName("title")[0].firstChild.nodeValue
        print(f"\nBook with id=2: {title}")

Note

Alternative: ElementTree For most use cases, xml.etree.ElementTree provides a simpler and more Pythonic API:

import xml.etree.ElementTree as ET

tree = ET.parse("catalogue.xml")
root = tree.getroot()

for book in root.findall("book"):
    title = book.find("title").text
    print(title)