Originally Posted by Python 2.4 Docs

13. Structured Markup Processing Tools
Python supports a variety of modules to work with various forms of structured data markup. This includes modules to work with the Standard Generalized Markup Language (SGML) and the Hypertext Markup Language (HTML), and several interfaces for working with the Extensible Markup Language (XML).
It is important to note that modules in the xml package require that there be at least one SAX-compliant XML parser available. Starting with Python 2.3, the Expat parser is included with Python, so the xml.parsers.expat module will always be available. You may still want to be aware of the PyXML add-on package; that package provides an extended set of XML libraries for Python.
The documentation for the xml.dom and xml.sax packages are the definition of the Python bindings for the DOM and SAX interfaces.
HTMLParser

A simple parser that can handle HTML and XHTML.
sgmllib

Only as much of an SGML parser as needed to parse HTML.
htmllib

A parser for HTML documents.
htmlentitydefs

Definitions of HTML general entities.
xml.parsers.expat

An interface to the Expat non-validating XML parser.
xml.dom

Document Object Model API for Python.
xml.dom.minidom

Lightweight Document Object Model (DOM) implementation.
xml.dom.pulldom

Support for building partial DOM trees from SAX events.
xml.sax

Package containing SAX2 base classes and convenience functions.
xml.sax.handler

Base classes for SAX event handlers.
xml.sax.saxutils

Convenience functions and classes for use with SAX.
xml.sax.xmlreader

Interface which SAX-compliant XML parsers must implement.
xmllib

A parser for XML documents.