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| </style><title>Python and bindings</title></head><body bgcolor="#8b7765" text="#000000" link="#000000" 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="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="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://garypennington.net/libxml2/">Solaris binaries</a></li><li><a href="http://www.zveno.com/open_source/libxml2xslt.html">MacOsX binaries</a></li><li><a href="http://sourceforge.net/projects/libxml2-pas/">Pascal 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 |
| 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> |
| (<a href="http://mail.gnome.org/archives/xml-bindings/">archives</a>) in |
| order to get updates to this list or to discuss the specific topic of libxml2 |
| or libxslt wrappers or bindings:</p><ul><li><a href="http://libxmlplusplus.sourceforge.net/">Libxml++</a> seems the |
| most up-to-date C++ bindings for libxml2, check the <a href="http://libxmlplusplus.sourceforge.net/reference/html/hierarchy.html">documentation</a> |
| and the <a href="http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/libxmlplusplus/libxml%2b%2b/examples/">examples</a>.</li> |
| <li>There is another <a href="http://libgdome-cpp.berlios.de/">C++ wrapper |
| based on the gdome2 bindings</a> maintained by Tobias Peters.</li> |
| <li>and a third C++ wrapper by Peter Jones <pjones@pmade.org> |
| <p>Website: <a href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p> |
| </li> |
| <li><a href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt |
| Sergeant</a> developed <a href="http://axkit.org/download/">XML::LibXSLT</a>, a Perl wrapper for |
| libxml2/libxslt as part of the <a href="http://axkit.com/">AxKit XML |
| application server</a>.</li> |
| <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 |
| Libxml2 Perl bindings.</li> |
| <li><a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a> provides an |
| earlier version of the libxml/libxslt <a href="http://www.rexx.com/~dkuhlman">wrappers for Python</a>.</li> |
| <li>Gopal.V and Peter Minten develop <a href="http://savannah.gnu.org/projects/libxmlsharp">libxml#</a>, a set of |
| C# libxml2 bindings.</li> |
| <li>Petr Kozelka provides <a href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue |
| libxml2</a> with Kylix, Delphi and other Pascal compilers.</li> |
| <li>Uwe Fechner also provides <a href="http://sourceforge.net/projects/idom2-pas/">idom2</a>, a DOM2 |
| implementation for Kylix2/D5/D6 from Borland.</li> |
| <li>Wai-Sun "Squidster" Chia provides <a href="http://www.rubycolor.org/arc/redist/">bindings for Ruby</a> and |
| libxml2 bindings are also available in Ruby through the <a href="http://libgdome-ruby.berlios.de/">libgdome-ruby</a> module |
| maintained by Tobias Peters.</li> |
| <li>Steve Ball and contributors maintains <a href="http://tclxml.sourceforge.net/">libxml2 and libxslt bindings for |
| Tcl</a>.</li> |
| <li>There is support for libxml2 in the DOM module of PHP.</li> |
| <li><a href="http://savannah.gnu.org/projects/classpathx/">LibxmlJ</a> is |
| an effort to create a 100% JAXP-compatible Java wrapper for libxml2 and |
| libxslt as part of GNU ClasspathX project.</li> |
| <li>Patrick McPhee provides Rexx bindings fof libxml2 and libxslt, look for |
| <a href="http://www.interlog.com/~ptjm/software.html">RexxXML</a>.</li> |
| </ul><p>The distribution includes a set of Python bindings, which are guaranteed |
| to be maintained as part of the library in the future, though the Python |
| interface have not yet reached the completeness of the C API.</p><p><a href="mailto:stephane.bidoul@softwareag.com">Stéphane Bidoul</a> |
| maintains <a href="http://users.skynet.be/sbi/libxml-python/">a Windows port |
| of the Python bindings</a>.</p><p>Note to people interested in building bindings, the API is formalized as |
| <a href="libxml2-api.xml">an XML API description file</a> which allows to |
| automate a large part of the Python bindings, this includes function |
| descriptions, enums, structures, typedefs, etc... The Python script used to |
| build the bindings is python/generator.py in the source distribution.</p><p>To install the Python bindings there are 2 options:</p><ul><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 |
| RPM</a> (and if needed the <a href="http://rpmfind.net/linux/rpm2html/search.php?query=libxslt-python">libxslt-python |
| RPM</a>).</li> |
| <li>Otherwise use the <a href="ftp://xmlsoft.org/python/">libxml2-python |
| module distribution</a> corresponding to your installed version of |
| libxml2 and libxslt. Note that to install it you will need both libxml2 |
| and libxslt installed and run "python setup.py build install" in the |
| module tree.</li> |
| </ul><p>The distribution includes a set of examples and regression tests for the |
| python bindings in the <code>python/tests</code> directory. Here are some |
| 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 |
| |
| doc = libxml2.parseFile("tst.xml") |
| if doc.name != "tst.xml": |
| print "doc.name failed" |
| sys.exit(1) |
| root = doc.children |
| if root.name != "doc": |
| print "root.name failed" |
| sys.exit(1) |
| child = root.children |
| if child.name != "foo": |
| print "child.name failed" |
| sys.exit(1) |
| doc.freeDoc()</pre><p>The Python module is called libxml2; parseFile is the equivalent of |
| xmlParseFile (most of the bindings are automatically generated, and the xml |
| prefix is removed and the casing convention are kept). All node seen at the |
| binding level share the same subset of accessors:</p><ul><li><code>name</code> : returns the node name</li> |
| <li><code>type</code> : returns a string indicating the node type</li> |
| <li><code>content</code> : returns the content of the node, it is based on |
| xmlNodeGetContent() and hence is recursive.</li> |
| <li><code>parent</code> , <code>children</code>, <code>last</code>, |
| <code>next</code>, <code>prev</code>, <code>doc</code>, |
| <code>properties</code>: pointing to the associated element in the tree, |
| those may return None in case no such link exists.</li> |
| </ul><p>Also note the need to explicitly deallocate documents with freeDoc() . |
| Reference counting for libxml2 trees would need quite a lot of work to |
| function properly, and rather than risk memory leaks if not implemented |
| correctly it sounds safer to have an explicit function to free a tree. The |
| wrapper python objects like doc, root or child are them automatically garbage |
| collected.</p><h3>validate.py:</h3><p>This test check the validation interfaces and redirection of error |
| messages:</p><pre>import libxml2 |
| |
| #deactivate error messages from the validation |
| def noerr(ctx, str): |
| pass |
| |
| libxml2.registerErrorHandler(noerr, None) |
| |
| ctxt = libxml2.createFileParserCtxt("invalid.xml") |
| ctxt.validate(1) |
| ctxt.parseDocument() |
| doc = ctxt.doc() |
| valid = ctxt.isValid() |
| doc.freeDoc() |
| if valid != 0: |
| print "validity check failed"</pre><p>The first thing to notice is the call to registerErrorHandler(), it |
| defines a new error handler global to the library. It is used to avoid seeing |
| 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 |
| createFileParserCtxt() and how the behaviour can be changed before calling |
| parseDocument() . Similarly the informations resulting from the parsing phase |
| are also available using context methods.</p><p>Contexts like nodes are defined as class and the libxml2 wrappers maps the |
| C function interfaces in terms of objects method as much as possible. The |
| best to get a complete view of what methods are supported is to look at the |
| 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 |
| |
| ctxt = libxml2.createPushParser(None, "<foo", 4, "test.xml") |
| ctxt.parseChunk("/>", 2, 1) |
| doc = ctxt.doc() |
| |
| doc.freeDoc()</pre><p>The context is created with a special call based on the |
| xmlCreatePushParser() from the C library. The first argument is an optional |
| SAX callback object, then the initial set of data, the length and the name of |
| 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 |
| 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 |
| the parser does not build a document, but provides callback information as |
| the parser makes progresses analyzing the data being provided:</p><pre>import libxml2 |
| log = "" |
| |
| class callback: |
| def startDocument(self): |
| global log |
| log = log + "startDocument:" |
| |
| def endDocument(self): |
| global log |
| log = log + "endDocument:" |
| |
| def startElement(self, tag, attrs): |
| global log |
| log = log + "startElement %s %s:" % (tag, attrs) |
| |
| def endElement(self, tag): |
| global log |
| log = log + "endElement %s:" % (tag) |
| |
| def characters(self, data): |
| global log |
| log = log + "characters: %s:" % (data) |
| |
| def warning(self, msg): |
| global log |
| log = log + "warning: %s:" % (msg) |
| |
| def error(self, msg): |
| global log |
| log = log + "error: %s:" % (msg) |
| |
| def fatalError(self, msg): |
| global log |
| log = log + "fatalError: %s:" % (msg) |
| |
| handler = callback() |
| |
| ctxt = libxml2.createPushParser(handler, "<foo", 4, "test.xml") |
| chunk = " url='tst'>b" |
| ctxt.parseChunk(chunk, len(chunk), 0) |
| chunk = "ar</foo>" |
| ctxt.parseChunk(chunk, len(chunk), 1) |
| |
| reference = "startDocument:startElement foo {'url': 'tst'}:" + \ |
| "characters: bar:endElement foo:endDocument:" |
| if log != reference: |
| print "Error got: %s" % log |
| print "Expected: %s" % reference</pre><p>The key object in that test is the handler, it provides a number of entry |
| points which can be called by the parser as it makes progresses to indicate |
| the information set obtained. The full set of callback is larger than what |
| the callback class in that specific example implements (see the SAX |
| definition for a complete list). The wrapper will only call those supplied by |
| the object when activated. The startElement receives the names of the element |
| and a dictionary containing the attributes carried by this element.</p><p>Also note that the reference string generated from the callback shows a |
| single character call even though the string "bar" is passed to the parser |
| 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 |
| |
| doc = libxml2.parseFile("tst.xml") |
| ctxt = doc.xpathNewContext() |
| res = ctxt.xpathEval("//*") |
| if len(res) != 2: |
| print "xpath query: wrong node set size" |
| sys.exit(1) |
| if res[0].name != "doc" or res[1].name != "foo": |
| print "xpath query: wrong node set value" |
| sys.exit(1) |
| doc.freeDoc() |
| ctxt.xpathFreeContext()</pre><p>This test parses a file, then create an XPath context to evaluate XPath |
| expression on it. The xpathEval() method execute an XPath query and returns |
| the result mapped in a Python way. String and numbers are natively converted, |
| and node sets are returned as a tuple of libxml2 Python nodes wrappers. Like |
| the document, the XPath context need to be freed explicitly, also not that |
| the result of the XPath query may point back to the document tree and hence |
| 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 |
| python:</p><pre>import libxml2 |
| |
| def foo(ctx, x): |
| return x + 1 |
| |
| doc = libxml2.parseFile("tst.xml") |
| ctxt = doc.xpathNewContext() |
| libxml2.registerXPathFunction(ctxt._o, "foo", None, foo) |
| res = ctxt.xpathEval("foo(1)") |
| if res != 2: |
| print "xpath extension failure" |
| doc.freeDoc() |
| ctxt.xpathFreeContext()</pre><p>Note how the extension function is registered with the context (but that |
| 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 |
| function can access the XPath evaluation context:</p><pre>def foo(ctx, x): |
| global called |
| |
| # |
| # test that access to the XPath evaluation contexts |
| # |
| pctxt = libxml2.xpathParserContext(_obj=ctx) |
| ctxt = pctxt.context() |
| called = ctxt.function() |
| return x + 1</pre><p>All the interfaces around the XPath parser(or rather evaluation) context |
| are not finalized, but it should be sufficient to do contextual work at the |
| evaluation point.</p><h3>Memory debugging:</h3><p>last but not least, all tests starts with the following prologue:</p><pre>#memory debug specific |
| libxml2.debugMemory(1)</pre><p>and ends with the following epilogue:</p><pre>#memory debug specific |
| libxml2.cleanupParser() |
| if libxml2.debugMemory(1) == 0: |
| print "OK" |
| else: |
| print "Memory leak %d bytes" % (libxml2.debugMemory(1)) |
| libxml2.dumpMemory()</pre><p>Those activate the memory debugging interface of libxml2 where all |
| allocated block in the library are tracked. The prologue then cleans up the |
| library state and checks that all allocated memory has been freed. If not it |
| 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> |