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| 10 | </style><title>Python and bindings</title></head><body bgcolor="#8b7765" text="#000000" link="#a06060" vlink="#000000"><table border="0" width="100%" cellpadding="5" cellspacing="0" align="center"><tr><td width="120"><a href="http://swpat.ffii.org/"><img src="epatents.png" alt="Action against software patents" /></a></td><td width="180"><a href="http://www.gnome.org/"><img src="gnome2.png" alt="Gnome2 Logo" /></a><a href="http://www.w3.org/Status"><img src="w3c.png" alt="W3C Logo" /></a><a href="http://www.redhat.com/"><img src="redhat.gif" alt="Red Hat Logo" /></a><div align="left"><a href="http://xmlsoft.org/"><img src="Libxml2-Logo-180x168.gif" alt="Made with Libxml2 Logo" /></a></div></td><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"><h1>The XML C parser and toolkit of Gnome</h1><h2>Python and bindings</h2></td></tr></table></td></tr></table></td></tr></table><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><td valign="top" width="200" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Developer Menu</b></center></td></tr><tr><td bgcolor="#fffacd"><form action="search.php" enctype="application/x-www-form-urlencoded" method="get"><input name="query" type="text" size="20" value="" /><input name="submit" type="submit" value="Search ..." /></form><ul><li><a href="index.html" style="font-weight:bold">Main Menu</a></li><li><a href="html/index.html" style="font-weight:bold">Reference Manual</a></li><li><a href="examples/index.html" style="font-weight:bold">Code Examples</a></li><li><a href="guidelines.html">XML Guidelines</a></li><li><a href="tutorial/index.html">Tutorial</a></li><li><a href="xmlreader.html">The Reader Interface</a></li><li><a href="ChangeLog.html">ChangeLog</a></li><li><a href="XSLT.html">XSLT</a></li><li><a href="python.html">Python and bindings</a></li><li><a href="architecture.html">libxml2 architecture</a></li><li><a href="tree.html">The tree output</a></li><li><a href="interface.html">The SAX interface</a></li><li><a href="xmlmem.html">Memory Management</a></li><li><a href="xmlio.html">I/O Interfaces</a></li><li><a href="library.html">The parser interfaces</a></li><li><a href="entities.html">Entities or no entities</a></li><li><a href="namespaces.html">Namespaces</a></li><li><a href="upgrade.html">Upgrading 1.x code</a></li><li><a href="threads.html">Thread safety</a></li><li><a href="DOM.html">DOM Principles</a></li><li><a href="example.html">A real example</a></li><li><a href="xml.html">flat page</a>, <a href="site.xsl">stylesheet</a></li></ul></td></tr></table><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>API Indexes</b></center></td></tr><tr><td bgcolor="#fffacd"><ul><li><a href="APIchunk0.html">Alphabetic</a></li><li><a href="APIconstructors.html">Constructors</a></li><li><a href="APIfunctions.html">Functions/Types</a></li><li><a href="APIfiles.html">Modules</a></li><li><a href="APIsymbols.html">Symbols</a></li></ul></td></tr></table><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Related links</b></center></td></tr><tr><td bgcolor="#fffacd"><ul><li><a href="http://mail.gnome.org/archives/xml/">Mail archive</a></li><li><a href="http://xmlsoft.org/XSLT/">XSLT libxslt</a></li><li><a href="http://phd.cs.unibo.it/gdome2/">DOM gdome2</a></li><li><a href="http://www.aleksey.com/xmlsec/">XML-DSig xmlsec</a></li><li><a href="ftp://xmlsoft.org/">FTP</a></li><li><a href="http://www.zlatkovic.com/projects/libxml/">Windows binaries</a></li><li><a href="http://opencsw.org/packages/libxml2">Solaris binaries</a></li><li><a href="http://www.explain.com.au/oss/libxml2xslt.html">MacOsX binaries</a></li><li><a href="http://lxml.de/">lxml Python bindings</a></li><li><a href="http://cpan.uwinnipeg.ca/dist/XML-LibXML">Perl bindings</a></li><li><a href="http://libxmlplusplus.sourceforge.net/">C++ bindings</a></li><li><a href="http://www.zend.com/php5/articles/php5-xmlphp.php#Heading4">PHP bindings</a></li><li><a href="http://sourceforge.net/projects/libxml2-pas/">Pascal bindings</a></li><li><a href="http://libxml.rubyforge.org/">Ruby bindings</a></li><li><a href="http://tclxml.sourceforge.net/">Tcl bindings</a></li><li><a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml2">Bug Tracker</a></li></ul></td></tr></table></td></tr></table></td><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"><p>There are a number of language bindings and wrappers available for
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| 11 | libxml2, the list below is not exhaustive. Please contact the <a href="http://mail.gnome.org/mailman/listinfo/xml-bindings">[email protected]</a>
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| 12 | (<a href="http://mail.gnome.org/archives/xml-bindings/">archives</a>) in
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| 13 | order to get updates to this list or to discuss the specific topic of libxml2
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| 14 | or libxslt wrappers or bindings:</p><ul>
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| 15 | <li><a href="http://libxmlplusplus.sourceforge.net/">Libxml++</a> seems the
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| 16 | most up-to-date C++ bindings for libxml2, check the <a href="http://libxmlplusplus.sourceforge.net/reference/html/hierarchy.html">documentation</a>
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| 17 | and the <a href="http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/libxmlplusplus/libxml%2b%2b/examples/">examples</a>.</li>
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| 18 | <li>There is another <a href="http://libgdome-cpp.berlios.de/">C++ wrapper
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| 19 | based on the gdome2 bindings</a> maintained by Tobias Peters.</li>
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| 20 | <li>and a third C++ wrapper by Peter Jones <[email protected]>
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| 21 | <p>Website: <a href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p>
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| 22 | </li>
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| 23 | <li>XML::LibXML <a href="http://cpan.uwinnipeg.ca/dist/XML-LibXML">Perl
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| 24 | bindings</a> are available on CPAN, as well as XML::LibXSLT
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| 25 | <a href="http://cpan.uwinnipeg.ca/dist/XML-LibXSLT">Perl libxslt
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| 26 | bindings</a>.</li>
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| 27 | <li>If you're interested into scripting XML processing, have a look at <a href="http://xsh.sourceforge.net/">XSH</a> an XML editing shell based on
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| 28 | Libxml2 Perl bindings.</li>
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| 29 | <li><a href="mailto:[email protected]">Dave Kuhlman</a> provides an
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| 30 | earlier version of the libxml/libxslt <a href="http://www.rexx.com/~dkuhlman">wrappers for Python</a>.</li>
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| 31 | <li>Gopal.V and Peter Minten develop <a href="http://savannah.gnu.org/projects/libxmlsharp">libxml#</a>, a set of
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| 32 | C# libxml2 bindings.</li>
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| 33 | <li>Petr Kozelka provides <a href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue
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| 34 | libxml2</a> with Kylix, Delphi and other Pascal compilers.</li>
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| 35 | <li>Uwe Fechner also provides <a href="http://sourceforge.net/projects/idom2-pas/">idom2</a>, a DOM2
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| 36 | implementation for Kylix2/D5/D6 from Borland.</li>
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| 37 | <li>There is <a href="http://libxml.rubyforge.org/">bindings for Ruby</a>
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| 38 | and libxml2 bindings are also available in Ruby through the <a href="http://libgdome-ruby.berlios.de/">libgdome-ruby</a> module
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| 39 | maintained by Tobias Peters.</li>
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| 40 | <li>Steve Ball and contributors maintains <a href="http://tclxml.sourceforge.net/">libxml2 and libxslt bindings for
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| 41 | Tcl</a>.</li>
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| 42 | <li>libxml2 and libxslt are the default XML libraries for PHP5.</li>
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| 43 | <li><a href="http://savannah.gnu.org/projects/classpathx/">LibxmlJ</a> is
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| 44 | an effort to create a 100% JAXP-compatible Java wrapper for libxml2 and
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| 45 | libxslt as part of GNU ClasspathX project.</li>
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| 46 | <li>Patrick McPhee provides Rexx bindings fof libxml2 and libxslt, look for
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| 47 | <a href="http://www.interlog.com/~ptjm/software.html">RexxXML</a>.</li>
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| 48 | <li><a href="http://www.satimage.fr/software/en/xml_suite.html">Satimage</a>
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| 49 | provides <a href="http://www.satimage.fr/software/en/downloads_osaxen.html">XMLLib
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| 50 | osax</a>. This is an osax for Mac OS X with a set of commands to
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| 51 | implement in AppleScript the XML DOM, XPATH and XSLT. Also includes
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| 52 | commands for Property-lists (Apple's fast lookup table XML format.)</li>
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| 53 | <li>Francesco Montorsi developped <a href="https://sourceforge.net/project/showfiles.php?group_id=51305&package_id=45182">wxXml2</a>
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| 54 | wrappers that interface libxml2, allowing wxWidgets applications to
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| 55 | load/save/edit XML instances.</li>
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| 56 | </ul><p>The distribution includes a set of Python bindings, which are guaranteed
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| 57 | to be maintained as part of the library in the future, though the Python
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| 58 | interface have not yet reached the completeness of the C API.</p><p>Note that some of the Python purist dislike the default set of Python
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| 59 | bindings, rather than complaining I suggest they have a look at <a href="http://lxml.de/">lxml the more pythonic bindings for libxml2
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| 60 | and libxslt</a> and <a href="http://lxml.de/mailinglist/">check the mailing-list</a>.</p><p><a href="mailto:[email protected]">Stéphane Bidoul</a>
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| 61 | maintains <a href="http://users.skynet.be/sbi/libxml-python/">a Windows port
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| 62 | of the Python bindings</a>.</p><p>Note to people interested in building bindings, the API is formalized as
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| 63 | <a href="libxml2-api.xml">an XML API description file</a> which allows to
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| 64 | automate a large part of the Python bindings, this includes function
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| 65 | descriptions, enums, structures, typedefs, etc... The Python script used to
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| 66 | build the bindings is python/generator.py in the source distribution.</p><p>To install the Python bindings there are 2 options:</p><ul>
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| 67 | <li>If you use an RPM based distribution, simply install the <a href="http://rpmfind.net/linux/rpm2html/search.php?query=libxml2-python">libxml2-python
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| 68 | RPM</a> (and if needed the <a href="http://rpmfind.net/linux/rpm2html/search.php?query=libxslt-python">libxslt-python
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| 69 | RPM</a>).</li>
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| 70 | <li>Otherwise use the <a href="ftp://xmlsoft.org/libxml2/python/">libxml2-python
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| 71 | module distribution</a> corresponding to your installed version of
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| 72 | libxml2 and libxslt. Note that to install it you will need both libxml2
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| 73 | and libxslt installed and run "python setup.py build install" in the
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| 74 | module tree.</li>
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| 75 | </ul><p>The distribution includes a set of examples and regression tests for the
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| 76 | python bindings in the <code>python/tests</code> directory. Here are some
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| 77 | excerpts from those tests:</p><h3>tst.py:</h3><p>This is a basic test of the file interface and DOM navigation:</p><pre>import libxml2, sys
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| 78 |
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| 79 | doc = libxml2.parseFile("tst.xml")
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| 80 | if doc.name != "tst.xml":
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| 81 | print "doc.name failed"
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| 82 | sys.exit(1)
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| 83 | root = doc.children
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| 84 | if root.name != "doc":
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| 85 | print "root.name failed"
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| 86 | sys.exit(1)
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| 87 | child = root.children
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| 88 | if child.name != "foo":
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| 89 | print "child.name failed"
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| 90 | sys.exit(1)
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| 91 | doc.freeDoc()</pre><p>The Python module is called libxml2; parseFile is the equivalent of
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| 92 | xmlParseFile (most of the bindings are automatically generated, and the xml
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| 93 | prefix is removed and the casing convention are kept). All node seen at the
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| 94 | binding level share the same subset of accessors:</p><ul>
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| 95 | <li><code>name</code> : returns the node name</li>
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| 96 | <li><code>type</code> : returns a string indicating the node type</li>
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| 97 | <li><code>content</code> : returns the content of the node, it is based on
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| 98 | xmlNodeGetContent() and hence is recursive.</li>
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| 99 | <li><code>parent</code> , <code>children</code>, <code>last</code>,
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| 100 | <code>next</code>, <code>prev</code>, <code>doc</code>,
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| 101 | <code>properties</code>: pointing to the associated element in the tree,
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| 102 | those may return None in case no such link exists.</li>
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| 103 | </ul><p>Also note the need to explicitly deallocate documents with freeDoc() .
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| 104 | Reference counting for libxml2 trees would need quite a lot of work to
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| 105 | function properly, and rather than risk memory leaks if not implemented
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| 106 | correctly it sounds safer to have an explicit function to free a tree. The
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| 107 | wrapper python objects like doc, root or child are them automatically garbage
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| 108 | collected.</p><h3>validate.py:</h3><p>This test check the validation interfaces and redirection of error
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| 109 | messages:</p><pre>import libxml2
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| 110 |
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| 111 | #deactivate error messages from the validation
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| 112 | def noerr(ctx, str):
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| 113 | pass
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| 114 |
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| 115 | libxml2.registerErrorHandler(noerr, None)
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| 116 |
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| 117 | ctxt = libxml2.createFileParserCtxt("invalid.xml")
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| 118 | ctxt.validate(1)
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| 119 | ctxt.parseDocument()
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| 120 | doc = ctxt.doc()
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| 121 | valid = ctxt.isValid()
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| 122 | doc.freeDoc()
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| 123 | if valid != 0:
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| 124 | print "validity check failed"</pre><p>The first thing to notice is the call to registerErrorHandler(), it
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| 125 | defines a new error handler global to the library. It is used to avoid seeing
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| 126 | the error messages when trying to validate the invalid document.</p><p>The main interest of that test is the creation of a parser context with
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| 127 | createFileParserCtxt() and how the behaviour can be changed before calling
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| 128 | parseDocument() . Similarly the information resulting from the parsing phase
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| 129 | is also available using context methods.</p><p>Contexts like nodes are defined as class and the libxml2 wrappers maps the
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| 130 | C function interfaces in terms of objects method as much as possible. The
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| 131 | best to get a complete view of what methods are supported is to look at the
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| 132 | libxml2.py module containing all the wrappers.</p><h3>push.py:</h3><p>This test show how to activate the push parser interface:</p><pre>import libxml2
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| 133 |
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| 134 | ctxt = libxml2.createPushParser(None, "<foo", 4, "test.xml")
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| 135 | ctxt.parseChunk("/>", 2, 1)
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| 136 | doc = ctxt.doc()
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| 137 |
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| 138 | doc.freeDoc()</pre><p>The context is created with a special call based on the
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| 139 | xmlCreatePushParser() from the C library. The first argument is an optional
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| 140 | SAX callback object, then the initial set of data, the length and the name of
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| 141 | the resource in case URI-References need to be computed by the parser.</p><p>Then the data are pushed using the parseChunk() method, the last call
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| 142 | setting the third argument terminate to 1.</p><h3>pushSAX.py:</h3><p>this test show the use of the event based parsing interfaces. In this case
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| 143 | the parser does not build a document, but provides callback information as
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| 144 | the parser makes progresses analyzing the data being provided:</p><pre>import libxml2
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| 145 | log = ""
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| 146 |
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| 147 | class callback:
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| 148 | def startDocument(self):
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| 149 | global log
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| 150 | log = log + "startDocument:"
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| 151 |
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| 152 | def endDocument(self):
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| 153 | global log
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| 154 | log = log + "endDocument:"
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| 155 |
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| 156 | def startElement(self, tag, attrs):
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| 157 | global log
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| 158 | log = log + "startElement %s %s:" % (tag, attrs)
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| 159 |
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| 160 | def endElement(self, tag):
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| 161 | global log
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| 162 | log = log + "endElement %s:" % (tag)
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| 163 |
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| 164 | def characters(self, data):
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| 165 | global log
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| 166 | log = log + "characters: %s:" % (data)
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| 167 |
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| 168 | def warning(self, msg):
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| 169 | global log
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| 170 | log = log + "warning: %s:" % (msg)
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| 171 |
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| 172 | def error(self, msg):
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| 173 | global log
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| 174 | log = log + "error: %s:" % (msg)
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| 175 |
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| 176 | def fatalError(self, msg):
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| 177 | global log
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| 178 | log = log + "fatalError: %s:" % (msg)
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| 179 |
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| 180 | handler = callback()
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| 181 |
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| 182 | ctxt = libxml2.createPushParser(handler, "<foo", 4, "test.xml")
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| 183 | chunk = " url='tst'>b"
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| 184 | ctxt.parseChunk(chunk, len(chunk), 0)
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| 185 | chunk = "ar</foo>"
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| 186 | ctxt.parseChunk(chunk, len(chunk), 1)
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| 187 |
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| 188 | reference = "startDocument:startElement foo {'url': 'tst'}:" + \
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| 189 | "characters: bar:endElement foo:endDocument:"
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| 190 | if log != reference:
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| 191 | print "Error got: %s" % log
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| 192 | print "Expected: %s" % reference</pre><p>The key object in that test is the handler, it provides a number of entry
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| 193 | points which can be called by the parser as it makes progresses to indicate
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| 194 | the information set obtained. The full set of callback is larger than what
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| 195 | the callback class in that specific example implements (see the SAX
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| 196 | definition for a complete list). The wrapper will only call those supplied by
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| 197 | the object when activated. The startElement receives the names of the element
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| 198 | and a dictionary containing the attributes carried by this element.</p><p>Also note that the reference string generated from the callback shows a
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| 199 | single character call even though the string "bar" is passed to the parser
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| 200 | from 2 different call to parseChunk()</p><h3>xpath.py:</h3><p>This is a basic test of XPath wrappers support</p><pre>import libxml2
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| 201 |
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| 202 | doc = libxml2.parseFile("tst.xml")
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| 203 | ctxt = doc.xpathNewContext()
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| 204 | res = ctxt.xpathEval("//*")
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| 205 | if len(res) != 2:
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| 206 | print "xpath query: wrong node set size"
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| 207 | sys.exit(1)
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| 208 | if res[0].name != "doc" or res[1].name != "foo":
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| 209 | print "xpath query: wrong node set value"
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| 210 | sys.exit(1)
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| 211 | doc.freeDoc()
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| 212 | ctxt.xpathFreeContext()</pre><p>This test parses a file, then create an XPath context to evaluate XPath
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| 213 | expression on it. The xpathEval() method execute an XPath query and returns
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| 214 | the result mapped in a Python way. String and numbers are natively converted,
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| 215 | and node sets are returned as a tuple of libxml2 Python nodes wrappers. Like
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| 216 | the document, the XPath context need to be freed explicitly, also not that
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| 217 | the result of the XPath query may point back to the document tree and hence
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| 218 | the document must be freed after the result of the query is used.</p><h3>xpathext.py:</h3><p>This test shows how to extend the XPath engine with functions written in
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| 219 | python:</p><pre>import libxml2
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| 220 |
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| 221 | def foo(ctx, x):
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| 222 | return x + 1
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| 223 |
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| 224 | doc = libxml2.parseFile("tst.xml")
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| 225 | ctxt = doc.xpathNewContext()
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| 226 | libxml2.registerXPathFunction(ctxt._o, "foo", None, foo)
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| 227 | res = ctxt.xpathEval("foo(1)")
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| 228 | if res != 2:
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| 229 | print "xpath extension failure"
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| 230 | doc.freeDoc()
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| 231 | ctxt.xpathFreeContext()</pre><p>Note how the extension function is registered with the context (but that
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| 232 | part is not yet finalized, this may change slightly in the future).</p><h3>tstxpath.py:</h3><p>This test is similar to the previous one but shows how the extension
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| 233 | function can access the XPath evaluation context:</p><pre>def foo(ctx, x):
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| 234 | global called
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| 235 |
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| 236 | #
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| 237 | # test that access to the XPath evaluation contexts
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| 238 | #
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| 239 | pctxt = libxml2.xpathParserContext(_obj=ctx)
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| 240 | ctxt = pctxt.context()
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| 241 | called = ctxt.function()
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| 242 | return x + 1</pre><p>All the interfaces around the XPath parser(or rather evaluation) context
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| 243 | are not finalized, but it should be sufficient to do contextual work at the
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| 244 | evaluation point.</p><h3>Memory debugging:</h3><p>last but not least, all tests starts with the following prologue:</p><pre>#memory debug specific
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| 245 | libxml2.debugMemory(1)</pre><p>and ends with the following epilogue:</p><pre>#memory debug specific
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| 246 | libxml2.cleanupParser()
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| 247 | if libxml2.debugMemory(1) == 0:
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| 248 | print "OK"
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| 249 | else:
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| 250 | print "Memory leak %d bytes" % (libxml2.debugMemory(1))
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| 251 | libxml2.dumpMemory()</pre><p>Those activate the memory debugging interface of libxml2 where all
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| 252 | allocated block in the library are tracked. The prologue then cleans up the
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| 253 | library state and checks that all allocated memory has been freed. If not it
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| 254 | calls dumpMemory() which saves that list in a <code>.memdump</code> file.</p><p><a href="bugs.html">Daniel Veillard</a></p></td></tr></table></td></tr></table></td></tr></table></td></tr></table></td></tr></table></body></html>
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