sam-t2/devtools/v9/html/python/lib/module-xml.dom.html

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<link rel="STYLESHEET" href="lib.css" type='text/css' />
<link rel="SHORTCUT ICON" href="../icons/pyfav.png" type="image/png" />
<link rel='start' href='../index.html' title='Python Documentation Index' />
<link rel="first" href="lib.html" title='Python Library Reference' />
<link rel='contents' href='contents.html' title="Contents" />
<link rel='index' href='genindex.html' title='Index' />
<link rel='last' href='about.html' title='About this document...' />
<link rel='help' href='about.html' title='About this document...' />
<link rel="next" href="module-xml.dom.minidom.html" />
<link rel="prev" href="module-xml.parsers.expat.html" />
<link rel="parent" href="markup.html" />
<link rel="next" href="node651.html" />
<meta name='aesop' content='information' />
<title>13.6 xml.dom -- The Document Object Model API</title>
</head>
<body>
<DIV CLASS="navigation">
<div id='top-navigation-panel' xml:id='top-navigation-panel'>
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="13.5.5 Expat error constants"
  href="expat-errors.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></A></td>
<td class='online-navigation'><a rel="parent" title="13. Structured Markup Processing"
  href="markup.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up One Level' width='32' /></A></td>
<td class='online-navigation'><a rel="next" title="13.6.1 Module Contents"
  href="node651.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></A></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></A></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></A></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="expat-errors.html">13.5.5 Expat error constants</A>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="markup.html">13. Structured Markup Processing</A>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="node651.html">13.6.1 Module Contents</A>
</div>
<hr /></div>
</DIV>
<!--End of Navigation Panel-->

<H1><A NAME="SECTION0015600000000000000000">
13.6 <tt class="module">xml.dom</tt> --
         The Document Object Model API</A>
</H1>

<P>
<A NAME="module-xml.dom"></A>

<P>

<span class="versionnote">New in version 2.0.</span>

<P>
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.

<P>
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.

<P>
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.

<P>
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&nbsp;2 recommendation.  The mapping of
the Level&nbsp;3 specification, currently only available in draft form, is
being developed by the <a class="ulink" href="http://www.python.org/sigs/xml-sig/"
  >Python XML Special Interest
Group</a> as part of the
<a class="ulink" href="http://pyxml.sourceforge.net/"
  >PyXML package</a>.  Refer to the
documentation bundled with that package for information on the current
state of DOM Level&nbsp;3 support.

<P>
DOM applications typically start by parsing some XML into a DOM.  How
this is accomplished is not covered at all by DOM Level&nbsp;1, and Level&nbsp;2
provides only limited improvements: There is a
<tt class="class">DOMImplementation</tt> object class which provides access to
<tt class="class">Document</tt> creation methods, but no way to access an XML
reader/parser/Document builder in an implementation-independent way.
There is also no well-defined way to access these methods without an
existing <tt class="class">Document</tt> object.  In Python, each DOM implementation
will provide a function <tt class="function">getDOMImplementation()</tt>. DOM Level&nbsp;3
adds a Load/Store specification, which defines an interface to the
reader, but this is not yet available in the Python standard library.

<P>
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.

<P>
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 <A href="dom-conformance.html#dom-conformance">13.6.3</A>,
``Conformance,'' for a detailed discussion of mapping requirements.

<P>
<div class="seealso">
  <p class="heading">See Also:</p>

  <dl compact="compact" class="seetitle">
    <dt><em class="citetitle"><a href="http://www.w3.org/TR/DOM-Level-2-Core/"
        >Document Object
            Model (DOM) Level&nbsp;2 Specification</a></em></dt>
    <dd>The W3C recommendation upon which the Python DOM API is
            based.</dd>
  </dl>
  <dl compact="compact" class="seetitle">
    <dt><em class="citetitle"><a href="http://www.w3.org/TR/REC-DOM-Level-1/"
        >Document Object
            Model (DOM) Level&nbsp;1 Specification</a></em></dt>
    <dd>The W3C recommendation for the
            DOM supported by <tt class="module">xml.dom.minidom</tt>.</dd>
  </dl>
  <dl compact="compact" class="seetitle">
    <dt><em class="citetitle"><a href="http://pyxml.sourceforge.net"
        >PyXML</a></em></dt>
    <dd>Users that require a
            full-featured implementation of DOM should use the PyXML
            package.</dd>
  </dl>
  <dl compact="compact" class="seetitle">
    <dt><em class="citetitle"><a href="http://www.omg.org/docs/formal/02-11-05.pdf"
        >Python
            Language Mapping Specification</a></em></dt>
    <dd>This specifies the mapping from OMG IDL to Python.</dd>
  </dl>
</div>

<P>

<p><br /></p><hr class='online-navigation' />
<div class='online-navigation'>
<!--Table of Child-Links-->
<A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></a>

<UL CLASS="ChildLinks">
<LI><A href="node651.html">13.6.1 Module Contents</a>
<LI><A href="node652.html">13.6.2 Objects in the DOM</a>
<UL>
<LI><A href="dom-implementation-objects.html">13.6.2.1 DOMImplementation Objects</a>
<LI><A href="dom-node-objects.html">13.6.2.2 Node Objects</a>
<LI><A href="dom-nodelist-objects.html">13.6.2.3 NodeList Objects</a>
<LI><A href="dom-documenttype-objects.html">13.6.2.4 DocumentType Objects</a>
<LI><A href="dom-document-objects.html">13.6.2.5 Document Objects</a>
<LI><A href="dom-element-objects.html">13.6.2.6 Element Objects</a>
<LI><A href="dom-attr-objects.html">13.6.2.7 Attr Objects</a>
<LI><A href="dom-attributelist-objects.html">13.6.2.8 NamedNodeMap Objects</a>
<LI><A href="dom-comment-objects.html">13.6.2.9 Comment Objects</a>
<LI><A href="dom-text-objects.html">13.6.2.10 Text and CDATASection Objects</a>
<LI><A href="dom-pi-objects.html">13.6.2.11 ProcessingInstruction Objects</a>
<LI><A href="dom-exceptions.html">13.6.2.12 Exceptions</a>
</ul>
<LI><A href="dom-conformance.html">13.6.3 Conformance</a>
<UL>
<LI><A href="dom-type-mapping.html">13.6.3.1 Type Mapping</a>
<LI><A href="dom-accessor-methods.html">13.6.3.2 Accessor Methods</a>
</ul></ul>
<!--End of Table of Child-Links-->
</div>

<DIV CLASS="navigation">
<div class='online-navigation'>
<p></p><hr />
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="13.5.5 Expat error constants"
  href="expat-errors.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></A></td>
<td class='online-navigation'><a rel="parent" title="13. Structured Markup Processing"
  href="markup.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up One Level' width='32' /></A></td>
<td class='online-navigation'><a rel="next" title="13.6.1 Module Contents"
  href="node651.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></A></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></A></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></A></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="expat-errors.html">13.5.5 Expat error constants</A>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="markup.html">13. Structured Markup Processing</A>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="node651.html">13.6.1 Module Contents</A>
</div>
</div>
<hr />
<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
</DIV>
<!--End of Navigation Panel-->
<ADDRESS>
See <i><a href="about.html">About this document...</a></i> for information on suggesting changes.
</ADDRESS>
</BODY>
</HTML>