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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
   11 libxml2, the list below is not exhaustive. Please contact the <a href="http://mail.gnome.org/mailman/listinfo/xml-bindings">xml-bindings@gnome.org</a>
   12 (<a href="http://mail.gnome.org/archives/xml-bindings/">archives</a>) in
   13 order to get updates to this list or to discuss the specific topic of libxml2
   14 or libxslt wrappers or bindings:</p><ul>
   15   <li><a href="http://libxmlplusplus.sourceforge.net/">Libxml++</a> seems the
   16     most up-to-date C++ bindings for libxml2, check the <a href="http://libxmlplusplus.sourceforge.net/reference/html/hierarchy.html">documentation</a>
   17     and the <a href="http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/libxmlplusplus/libxml%2b%2b/examples/">examples</a>.</li>
   18   <li>There is another <a href="http://libgdome-cpp.berlios.de/">C++ wrapper
   19     based on the gdome2 bindings</a> maintained by Tobias Peters.</li>
   20   <li>and a third C++ wrapper by Peter Jones &lt;pjones@pmade.org&gt;
   21     <p>Website: <a href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p>
   22   </li>
   23   <li>XML::LibXML <a href="http://cpan.uwinnipeg.ca/dist/XML-LibXML">Perl
   24       bindings</a> are available on CPAN, as well as XML::LibXSLT
   25       <a href="http://cpan.uwinnipeg.ca/dist/XML-LibXSLT">Perl libxslt
   26       bindings</a>.</li>
   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
   28     Libxml2 Perl bindings.</li>
   29   <li><a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a> provides an
   30     earlier version of the libxml/libxslt <a href="http://www.rexx.com/~dkuhlman">wrappers for Python</a>.</li>
   31   <li>Gopal.V and Peter Minten develop <a href="http://savannah.gnu.org/projects/libxmlsharp">libxml#</a>, a set of
   32     C# libxml2 bindings.</li>
   33   <li>Petr Kozelka provides <a href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue
   34     libxml2</a> with Kylix, Delphi and other Pascal compilers.</li>
   35   <li>Uwe Fechner also provides <a href="http://sourceforge.net/projects/idom2-pas/">idom2</a>, a DOM2
   36     implementation for Kylix2/D5/D6 from Borland.</li>
   37   <li>There is <a href="http://libxml.rubyforge.org/">bindings for Ruby</a> 
   38     and libxml2 bindings are also available in Ruby through the <a href="http://libgdome-ruby.berlios.de/">libgdome-ruby</a> module
   39     maintained by Tobias Peters.</li>
   40   <li>Steve Ball and contributors maintains <a href="http://tclxml.sourceforge.net/">libxml2 and libxslt bindings for
   41     Tcl</a>.</li>
   42   <li>libxml2 and libxslt are the default XML libraries for PHP5.</li>
   43   <li><a href="http://savannah.gnu.org/projects/classpathx/">LibxmlJ</a> is
   44     an effort to create a 100% JAXP-compatible Java wrapper for libxml2 and
   45     libxslt as part of GNU ClasspathX project.</li>
   46   <li>Patrick McPhee provides Rexx bindings fof libxml2 and libxslt, look for
   47     <a href="http://www.interlog.com/~ptjm/software.html">RexxXML</a>.</li>
   48   <li><a href="http://www.satimage.fr/software/en/xml_suite.html">Satimage</a>
   49     provides <a href="http://www.satimage.fr/software/en/downloads_osaxen.html">XMLLib
   50     osax</a>. This is an osax for Mac OS X with a set of commands to
   51     implement in AppleScript the XML DOM, XPATH and XSLT. Also includes
   52     commands for Property-lists (Apple's fast lookup table XML format.)</li>
   53   <li>Francesco Montorsi developped <a href="https://sourceforge.net/project/showfiles.php?group_id=51305&amp;package_id=45182">wxXml2</a>
   54     wrappers that interface libxml2, allowing wxWidgets applications to
   55     load/save/edit XML instances.</li>
   56 </ul><p>The distribution includes a set of Python bindings, which are guaranteed
   57 to be maintained as part of the library in the future, though the Python
   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
   59 bindings, rather than complaining I suggest they have a look at <a href="http://lxml.de/">lxml the more pythonic bindings for libxml2
   60 and libxslt</a> and <a href="http://lxml.de/mailinglist/">check the mailing-list</a>.</p><p><a href="mailto:stephane.bidoul@softwareag.com">Stéphane Bidoul</a>
   61 maintains <a href="http://users.skynet.be/sbi/libxml-python/">a Windows port
   62 of the Python bindings</a>.</p><p>Note to people interested in building bindings, the API is formalized as
   63 <a href="libxml2-api.xml">an XML API description file</a> which allows to
   64 automate a large part of the Python bindings, this includes function
   65 descriptions, enums, structures, typedefs, etc... The Python script used to
   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>
   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
   68     RPM</a> (and if needed the <a href="http://rpmfind.net/linux/rpm2html/search.php?query=libxslt-python">libxslt-python
   69     RPM</a>).</li>
   70   <li>Otherwise use the <a href="ftp://xmlsoft.org/libxml2/python/">libxml2-python
   71     module distribution</a> corresponding to your installed version of
   72     libxml2 and libxslt. Note that to install it you will need both libxml2
   73     and libxslt installed and run "python setup.py build install" in the
   74     module tree.</li>
   75 </ul><p>The distribution includes a set of examples and regression tests for the
   76 python bindings in the <code>python/tests</code> directory. Here are some
   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
   78 
   79 doc = libxml2.parseFile("tst.xml")
   80 if doc.name != "tst.xml":
   81     print "doc.name failed"
   82     sys.exit(1)
   83 root = doc.children
   84 if root.name != "doc":
   85     print "root.name failed"
   86     sys.exit(1)
   87 child = root.children
   88 if child.name != "foo":
   89     print "child.name failed"
   90     sys.exit(1)
   91 doc.freeDoc()</pre><p>The Python module is called libxml2; parseFile is the equivalent of
   92 xmlParseFile (most of the bindings are automatically generated, and the xml
   93 prefix is removed and the casing convention are kept). All node seen at the
   94 binding level share the same subset of accessors:</p><ul>
   95   <li><code>name</code> : returns the node name</li>
   96   <li><code>type</code> : returns a string indicating the node type</li>
   97   <li><code>content</code> : returns the content of the node, it is based on
   98     xmlNodeGetContent() and hence is recursive.</li>
   99   <li><code>parent</code> , <code>children</code>, <code>last</code>,
  100     <code>next</code>, <code>prev</code>, <code>doc</code>,
  101     <code>properties</code>: pointing to the associated element in the tree,
  102     those may return None in case no such link exists.</li>
  103 </ul><p>Also note the need to explicitly deallocate documents with freeDoc() .
  104 Reference counting for libxml2 trees would need quite a lot of work to
  105 function properly, and rather than risk memory leaks if not implemented
  106 correctly it sounds safer to have an explicit function to free a tree. The
  107 wrapper python objects like doc, root or child are them automatically garbage
  108 collected.</p><h3>validate.py:</h3><p>This test check the validation interfaces and redirection of error
  109 messages:</p><pre>import libxml2
  110 
  111 #deactivate error messages from the validation
  112 def noerr(ctx, str):
  113     pass
  114 
  115 libxml2.registerErrorHandler(noerr, None)
  116 
  117 ctxt = libxml2.createFileParserCtxt("invalid.xml")
  118 ctxt.validate(1)
  119 ctxt.parseDocument()
  120 doc = ctxt.doc()
  121 valid = ctxt.isValid()
  122 doc.freeDoc()
  123 if valid != 0:
  124     print "validity check failed"</pre><p>The first thing to notice is the call to registerErrorHandler(), it
  125 defines a new error handler global to the library. It is used to avoid seeing
  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
  127 createFileParserCtxt() and how the behaviour can be changed before calling
  128 parseDocument() . Similarly the information resulting from the parsing phase
  129 is also available using context methods.</p><p>Contexts like nodes are defined as class and the libxml2 wrappers maps the
  130 C function interfaces in terms of objects method as much as possible. The
  131 best to get a complete view of what methods are supported is to look at the
  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
  133 
  134 ctxt = libxml2.createPushParser(None, "&lt;foo", 4, "test.xml")
  135 ctxt.parseChunk("/&gt;", 2, 1)
  136 doc = ctxt.doc()
  137 
  138 doc.freeDoc()</pre><p>The context is created with a special call based on the
  139 xmlCreatePushParser() from the C library. The first argument is an optional
  140 SAX callback object, then the initial set of data, the length and the name of
  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
  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
  143 the parser does not build a document, but provides callback information as
  144 the parser makes progresses analyzing the data being provided:</p><pre>import libxml2
  145 log = ""
  146 
  147 class callback:
  148     def startDocument(self):
  149         global log
  150         log = log + "startDocument:"
  151 
  152     def endDocument(self):
  153         global log
  154         log = log + "endDocument:"
  155 
  156     def startElement(self, tag, attrs):
  157         global log
  158         log = log + "startElement %s %s:" % (tag, attrs)
  159 
  160     def endElement(self, tag):
  161         global log
  162         log = log + "endElement %s:" % (tag)
  163 
  164     def characters(self, data):
  165         global log
  166         log = log + "characters: %s:" % (data)
  167 
  168     def warning(self, msg):
  169         global log
  170         log = log + "warning: %s:" % (msg)
  171 
  172     def error(self, msg):
  173         global log
  174         log = log + "error: %s:" % (msg)
  175 
  176     def fatalError(self, msg):
  177         global log
  178         log = log + "fatalError: %s:" % (msg)
  179 
  180 handler = callback()
  181 
  182 ctxt = libxml2.createPushParser(handler, "&lt;foo", 4, "test.xml")
  183 chunk = " url='tst'&gt;b"
  184 ctxt.parseChunk(chunk, len(chunk), 0)
  185 chunk = "ar&lt;/foo&gt;"
  186 ctxt.parseChunk(chunk, len(chunk), 1)
  187 
  188 reference = "startDocument:startElement foo {'url': 'tst'}:" + \ 
  189             "characters: bar:endElement foo:endDocument:"
  190 if log != reference:
  191     print "Error got: %s" % log
  192     print "Expected: %s" % reference</pre><p>The key object in that test is the handler, it provides a number of entry
  193 points which can be called by the parser as it makes progresses to indicate
  194 the information set obtained. The full set of callback is larger than what
  195 the callback class in that specific example implements (see the SAX
  196 definition for a complete list). The wrapper will only call those supplied by
  197 the object when activated. The startElement receives the names of the element
  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
  199 single character call even though the string "bar" is passed to the parser
  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
  201 
  202 doc = libxml2.parseFile("tst.xml")
  203 ctxt = doc.xpathNewContext()
  204 res = ctxt.xpathEval("//*")
  205 if len(res) != 2:
  206     print "xpath query: wrong node set size"
  207     sys.exit(1)
  208 if res[0].name != "doc" or res[1].name != "foo":
  209     print "xpath query: wrong node set value"
  210     sys.exit(1)
  211 doc.freeDoc()
  212 ctxt.xpathFreeContext()</pre><p>This test parses a file, then create an XPath context to evaluate XPath
  213 expression on it. The xpathEval() method execute an XPath query and returns
  214 the result mapped in a Python way. String and numbers are natively converted,
  215 and node sets are returned as a tuple of libxml2 Python nodes wrappers. Like
  216 the document, the XPath context need to be freed explicitly, also not that
  217 the result of the XPath query may point back to the document tree and hence
  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
  219 python:</p><pre>import libxml2
  220 
  221 def foo(ctx, x):
  222     return x + 1
  223 
  224 doc = libxml2.parseFile("tst.xml")
  225 ctxt = doc.xpathNewContext()
  226 libxml2.registerXPathFunction(ctxt._o, "foo", None, foo)
  227 res = ctxt.xpathEval("foo(1)")
  228 if res != 2:
  229     print "xpath extension failure"
  230 doc.freeDoc()
  231 ctxt.xpathFreeContext()</pre><p>Note how the extension function is registered with the context (but that
  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
  233 function can access the XPath evaluation context:</p><pre>def foo(ctx, x):
  234     global called
  235 
  236     #
  237     # test that access to the XPath evaluation contexts
  238     #
  239     pctxt = libxml2.xpathParserContext(_obj=ctx)
  240     ctxt = pctxt.context()
  241     called = ctxt.function()
  242     return x + 1</pre><p>All the interfaces around the XPath parser(or rather evaluation) context
  243 are not finalized, but it should be sufficient to do contextual work at the
  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
  245 libxml2.debugMemory(1)</pre><p>and ends with the following epilogue:</p><pre>#memory debug specific
  246 libxml2.cleanupParser()
  247 if libxml2.debugMemory(1) == 0:
  248     print "OK"
  249 else:
  250     print "Memory leak %d bytes" % (libxml2.debugMemory(1))
  251     libxml2.dumpMemory()</pre><p>Those activate the memory debugging interface of libxml2 where all
  252 allocated block in the library are tracked. The prologue then cleans up the
  253 library state and checks that all allocated memory has been freed. If not it
  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>