Python Cookbook

Chapter 12. Processing XML

Introduction

Credit: Paul Prescod, co-author of XML Handbook (Prentice Hall)

XML has become a central technology for all kinds of information exchange. Today, most new file formats that are invented are based on XML. Most new protocols are based upon XML. It simply isn’t possible to work with the emerging Internet infrastructure without supporting XML. Luckily, Python has had XML support since Version 2.0.

Python and XML are perfect complements for each other. XML is an open-standards way of exchanging information. Python is an open source language that processes the information. Python is strong at text processing and at handling complicated data structures. XML is text-based and is a way of exchanging complicated data structures.

That said, working with XML is not so seamless that it takes no effort. There is always somewhat of a mismatch between the needs of a particular programming language and a language-independent information representation. So there is often a requirement to write code that reads (deserializes or parses) and writes (serializes) XML.

Parsing XML can be done with code written purely in Python or with a module that is a C/Python mix. Python comes with the fast Expat parser written in C. This is what most XML applications use. Recipe 12.7 shows how to use Expat directly with its native API.

Although Expat is ubiquitous in the XML world, it is not the only parser available. There is an API called SAX that allows any XML parser to be plugged ...