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https://gitlab.gnome.org/GNOME/libxslt
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272 lines
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HTML
272 lines
13 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/1999/REC-html401-19991224/loose.dtd">
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<html>
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<head>
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<meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type">
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<style type="text/css"><!--
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TD {font-size: 14pt; font-family: Verdana,Arial,Helvetica}
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BODY {font-size: 14pt; font-family: Verdana,Arial,Helvetica; margin-top: 2em; margin-left: 0em; margin-right: 0em}
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H1 {font-size: 20pt; font-family: Verdana,Arial,Helvetica}
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H2 {font-size: 18pt; font-family: Verdana,Arial,Helvetica}
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H3 {font-size: 16pt; font-family: Verdana,Arial,Helvetica}
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A:link, A:visited, A:active { text-decoration: underline }
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--></style>
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<title>Python and bindings</title>
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</head>
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<body bgcolor="#8b7765" text="#000000" link="#000000" vlink="#000000">
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<table border="0" width="100%" cellpadding="5" cellspacing="0" align="center"><tr>
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<td width="100">
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<a href="http://www.gnome.org/"><img src="smallfootonly.gif" alt="Gnome Logo"></a><a href="http://www.redhat.com"><img src="redhat.gif" alt="Red Hat Logo"></a>
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</td>
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<td><table border="0" width="90%" cellpadding="2" cellspacing="0" align="center" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3" bgcolor="#fffacd"><tr><td align="center">
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<h1>The XSLT C library for Gnome</h1>
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<h2>Python and bindings</h2>
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</td></tr></table></td></tr></table></td>
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</tr></table>
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<table border="0" cellpadding="4" cellspacing="0" width="100%" align="center"><tr><td bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr>
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<td valign="top" width="200" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td>
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<table width="100%" border="0" cellspacing="1" cellpadding="3">
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<tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Main Menu</b></center></td></tr>
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<tr><td bgcolor="#fffacd"><ul>
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<li><a href="index.html">Home</a></li>
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<li><a href="intro.html">Introduction</a></li>
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<li><a href="docs.html">Documentation</a></li>
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<li><a href="bugs.html">Reporting bugs and getting help</a></li>
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<li><a href="help.html">How to help</a></li>
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<li><a href="downloads.html">Downloads</a></li>
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<li><a href="FAQ.html">FAQ</a></li>
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<li><a href="news.html">News</a></li>
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<li><a href="xsltproc2.html">The xsltproc tool</a></li>
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<li><a href="docbook.html">DocBook</a></li>
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<li><a href="API.html">The programming API</a></li>
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<li><a href="python.html">Python and bindings</a></li>
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<li><a href="internals.html">Library internals</a></li>
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<li><a href="extensions.html">Writing extensions</a></li>
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<li><a href="contribs.html">Contributions</a></li>
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<li>
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<a href="xslt.html">flat page</a>, <a href="site.xsl">stylesheet</a>
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</li>
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</ul></td></tr>
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</table>
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<table width="100%" border="0" cellspacing="1" cellpadding="3">
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<tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>API Indexes</b></center></td></tr>
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<tr><td bgcolor="#fffacd"><ul>
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<li><a href="APIchunk0.html">Alphabetic</a></li>
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<li><a href="APIconstructors.html">Constructors</a></li>
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<li><a href="APIfunctions.html">Functions/Types</a></li>
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<li><a href="APIfiles.html">Modules</a></li>
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<li><a href="APIsymbols.html">Symbols</a></li>
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</ul></td></tr>
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</table>
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<table width="100%" border="0" cellspacing="1" cellpadding="3">
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<tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Related links</b></center></td></tr>
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<tr><td bgcolor="#fffacd"><ul>
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<li><a href="tutorial/libxslttutorial.html">Tutorial</a></li>
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<li><a href="xsltproc.html">Man page for xsltproc</a></li>
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<li><a href="http://mail.gnome.org/archives/xslt/">Mail archive</a></li>
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<li><a href="http://xmlsoft.org/">XML libxml</a></li>
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<li><a href="http://phd.cs.unibo.it/gdome2/">DOM gdome2</a></li>
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<li><a href="ftp://xmlsoft.org/">FTP</a></li>
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<li><a href="http://www.fh-frankfurt.de/~igor/projects/libxml/">Windows binaries</a></li>
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<li><a href="http://garypennington.net/libxml2/">Solaris binaries</a></li>
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<li><a href="http://bugzilla.gnome.org/buglist.cgi?product=libxslt">Bug Tracker</a></li>
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<li><a href="http://xsldbg.sourceforge.net/">Xsldbg Debugger</a></li>
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</ul></td></tr>
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</table>
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</td></tr></table></td>
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<td valign="top" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%"><tr><td><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table border="0" cellpadding="3" cellspacing="1" width="100%"><tr><td bgcolor="#fffacd">
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<p>There is a number of language bindings and wrappers available for libxml2,
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the list below is not exhaustive. Please contact the <a href="http://mail.gnome.org/mailman/listinfo/xml-bindings">xml-bindings@gnome.org</a>
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(<a href="http://mail.gnome.org/archives/xml-bindings/">archives</a>) in
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order to get updates to this list or to discuss the specific topic of libxml2
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or libxslt wrappers or bindings:</p>
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<ul>
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<li>
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<a href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt
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Sergeant</a>
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developped <a href="http://axkit.org/download/">XML::LibXML and
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XML::LibXSLT</a>, a perl wrapper for libxml2/libxslt as part of the <a href="http://axkit.com/">AxKit XML application server</a>
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</li>
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<li>
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<a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a>
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provides and earlier version of the libxml/libxslt <a href="http://www.rexx.com/~dkuhlman">wrappers for Python</a>
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</li>
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<li>Petr Kozelka provides <a href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue
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libxml2</a> with Kylix, Delphi and other Pascal compilers</li>
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<li>Wai-Sun "Squidster" Chia provides <a href="http://www.rubycolor.org/arc/redist/">bindings for Ruby</a> and
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libxml2 bindings are also available in Ruby through the <a href="http://libgdome-ruby.berlios.de/">libgdome-ruby</a> module
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maintained by Tobias Peters.</li>
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<li>Steve Ball and contributors maintains
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<a href="http://tclxml.sourceforge.net/">libxml2 and libxslt bindings for
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Tcl</a>
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</li>
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</ul>
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<p>The libxslt Python module depends on the <a href="http://xmlsoft.org/python.html">libxml2 Python</a> module.
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</p>
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<p>The distribution includes a set of Python bindings, which are garanteed to
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be maintained as part of the library in the future, though the Python
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interface have not yet reached the maturity of the C API. The distribution
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includes a set of examples and regression tests for the python bindings in
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the <code>python/tests</code> directory. Here are some excepts from those
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tests:</p>
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<h3>basic.py:</h3>
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<p>This is a basic test of XSLT interfaces: loading a stylesheet and
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a document, transforming the document and saving the result.</p>
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<pre>import libxml2
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import libxslt
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styledoc = libxml2.parseFile("test.xsl")
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style = libxslt.parseStylesheetDoc(styledoc)
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doc = libxml2.parseFile("test.xml")
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result = style.applyStylesheet(doc, None)
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style.saveResultToFilename("foo", result, 0)
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style.freeStylesheet()
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doc.freeDoc()
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result.freeDoc()</pre>
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<p>The Python module is called libxslt, you will also need the libxml2 module
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for the operations on XML trees. Let's have a look at the objects manipulated
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in that example and how is the processing done:</p>
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<ul>
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<li>
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<code>styledoc</code>: is a libxml2 document tree. It is obtained by
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parsing the XML file "test.xsl" containing the stylesheet.</li>
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<li>
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<code>style</code>: this is a precompiled stylesheet ready to be used
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by the following transformations (note the plural form, multiple
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transformations can resuse the same stylesheet).</li>
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<li>
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<code>doc</code>: this is the document to apply the transformation to.
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In this case it is simply generated by parsing it from a file but any
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other processing is possible as long as one get a libxml2 Doc. Note
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that HTML tree are suitable for XSLT processing in libxslt. This is
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actually how this page is generated !</li>
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<li>
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<code>result</code>: this is a document generated by applying the
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stylesheet to the document. Note that some of the stylesheet informations
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may be related to the serialization of that document and as in this
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example a specific saveResultToFilename() method of the stylesheet
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should be used to save it to a file (in that case to "foo").</li>
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</ul>
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<p>Also note the need to explicitely deallocate documents with freeDoc()
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except for the stylesheet document which is freed when its compiled form
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is garbage collected.</p>
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<h3>extfunc.py:</h3>
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<p>This one is a far more complex test. It shows how to modify the behaviour
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of an XSLT transformation by passing parameters and how to extend the XSLT
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engine with functions defined in python:</p>
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<pre>import libxml2
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import libxslt
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import string
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nodeName = None
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def f(ctx, str):
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global nodeName
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#
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# Small check to verify the context is correcly accessed
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#
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try:
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pctxt = libxslt.xpathParserContext(_obj=ctx)
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ctxt = pctxt.context()
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tctxt = ctxt.transformContext()
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nodeName = tctxt.insertNode().name
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except:
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pass
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return string.upper(str)
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libxslt.registerExtModuleFunction("foo", "http://example.com/foo", f)</pre>
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<p> This code defines and register an extension function. Note that the
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function can be bound to any name (foo) and how the binding is also
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associated to a namespace name "http://example.com/foo". From an
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XSLT point of view the function just returns an upper case version of the
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string passed as a parameter. But the first part of the function also
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read some contextual information from the current XSLT processing environement,
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in that case it looks for the current insertion node in the resulting output
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(either the resulting document or the Result Value Tree being generated), and
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saves it to a global variable for checking that the access actually worked.
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</p>
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<p> For more informations on the xpathParserContext and transformContext
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objects check the <a href="internals.html">libray internals description</a>.
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The pctxt is actually an object from a class derived from the
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libxml2.xpathParserContext() with just a couple more properties including
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the possibility to look up the XSLT transformation context from the XPath
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context.
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</p>
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<pre>
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styledoc = libxml2.parseDoc("""
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<xsl:stylesheet version='1.0'
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xmlns:xsl='http://www.w3.org/1999/XSL/Transform'
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xmlns:foo='http://example.com/foo'
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xsl:exclude-result-prefixes='foo'>
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<xsl:param name='bar'>failure</xsl:param>
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<xsl:template match='/'>
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<article><xsl:value-of select='foo:foo($bar)'/></article>
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</xsl:template>
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</xsl:stylesheet>
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""")</pre>
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<p> Here is a simple example of how to read an XML document from a python
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string with libxml2. Note how this stylesheet:
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</p>
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<ul>
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<li> Uses a global parameter <code>bar</code>
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</li>
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<li> Reference the extension function f
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</li>
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<li> how the Namespace name "http://example.com/foo" has to be bound to
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a prefix
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</li>
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<li> how that prefix is excluded from the output
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</li>
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<li> how the function is called from the select
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</li>
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</ul>
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<pre>style = libxslt.parseStylesheetDoc(styledoc)
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doc = libxml2.parseDoc("<doc/>")
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result = style.applyStylesheet(doc, { "bar": "'success'" })
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style.freeStylesheet()
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doc.freeDoc()</pre>
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<p> that part is identical, to the basic example except that the
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transformation is passed a dictionnary of parameters. Note that the
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string passed "success" had to be quoted, otherwise it is interpreted
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as an XPath query for the childs of root named "success".
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</p>
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<pre>
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root = result.children
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if root.name != "article":
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print "Unexpected root node name"
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sys.exit(1)
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if root.content != "SUCCESS":
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print "Unexpected root node content, extension function failed"
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sys.exit(1)
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if nodeName != 'article':
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print "The function callback failed to access its context"
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sys.exit(1)
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result.freeDoc()
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</pre>
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<p> That part just verifies that the transformation worked, that the parameter
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got properly passed to the engine, that the function f() got called and that
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it properly accessed the context to find the name of the insertion node.
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</p>
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<h3>pyxsltproc.py:</h3>
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<p> this module is a bit too long to be described there but it is basically
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a rewrite of the xsltproc command line interface of libxslt in Python. It
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provides nearly all the functionalities of xsltproc and can be used as a base
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module to write Python customized XSLT processors. One of the thing
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to notice are:
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</p>
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<pre>libxml2.lineNumbersDefault(1)
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libxml2.substituteEntitiesDefault(1)
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</pre>
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<p> those two calls in the main() function are needed to force the libxml2
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processor to generate DOM trees compliant with the XPath data model.
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</p>
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<p><a href="mailto:daniel@veillard.com">Daniel Veillard</a></p>
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</td></tr></table></td></tr></table></td></tr></table></td>
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</tr></table></td></tr></table>
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</body>
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</html>
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