GNU Info

(python2.1-lib.info)xml.dom

---

Next: xml.dom.minidom Prev: xml.parsers.expat Up: Structured Markup Processing Tools

---

Enter node , (file) or (file)node

The Document Object Model API
=============================

Document Object Model API for Python.

This manual section was written by Paul Prescod <paul@prescod.net>.
This manual section was written by Martin v. L"owis
<loewis@informatik.hu-berlin.de>.
_Added in Python version 2.0_

The Document Object Model, or "DOM," is a cross-language API from the
World Wide Web Consortium (W3C) for accessing and modifying XML
documents.  A DOM implementation presents an XML document as a tree
structure, or allows client code to build such a structure from
scratch.  It then gives access to the structure through a set of
objects which provided well-known interfaces.

The DOM is extremely useful for random-access applications.  SAX only
allows you a view of one bit of the document at a time.  If you are
looking at one SAX element, you have no access to another.  If you are
looking at a text node, you have no access to a containing element.
When you write a SAX application, you need to keep track of your
program's position in the document somewhere in your own code.  SAX
does not do it for you.  Also, if you need to look ahead in the XML
document, you are just out of luck.

Some applications are simply impossible in an event driven model with
no access to a tree.  Of course you could build some sort of tree
yourself in SAX events, but the DOM allows you to avoid writing that
code.  The DOM is a standard tree representation for XML data.

The Document Object Model is being defined by the W3C in stages, or
"levels" in their terminology.  The Python mapping of the API is
substantially based on the DOM Level 2 recommendation.  Some aspects of
the API will only become available in Python 2.1, or may only be
available in particular DOM implementations.

DOM applications typically start by parsing some XML into a DOM.  How
this is accomplished is not covered at all by DOM Level 1, and Level 2
provides only limited improvements.  There is a `DOMImplementation'
object class which provides access to `Document' creation methods, but
these methods were only added in DOM Level 2 and were not implemented
in time for Python 2.0.  There is also no well-defined way to access
these methods without an existing `Document' object.  For Python 2.0,
consult the documentation for each particular DOM implementation to
determine the bootstrap procedure needed to create and initialize
`Document' and `DocumentType' instances.

Once you have a DOM document object, you can access the parts of your
XML document through its properties and methods.  These properties are
defined in the DOM specification; this portion of the reference manual
describes the interpretation of the specification in Python.

The specification provided by the W3C defines the DOM API for Java,
ECMAScript, and OMG IDL.  The Python mapping defined here is based in
large part on the IDL version of the specification, but strict
compliance is not required (though implementations are free to support
the strict mapping from IDL).  See section Note: Conformance,
"Conformance," for a detailed discussion of mapping requirements.

See also:
     `Document Object Model (DOM) Level 2 Specification' {The W3C
     recommendation upon which the Python DOM API is based.} `Document
     Object Model (DOM) Level 1 Specification' {The W3C recommendation
     for the DOM supported by `xml.dom.minidom'.} `PyXML'{Users that
     require a full-featured implementation of DOM should use the PyXML
     package.} `CORBA Scripting with Python' {This specifies the
     mapping from OMG IDL to Python.}

Module Contents 2

Objects in the DOM

Conformance