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				13	<title>Python and bindings</title>
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				21	<h1>The XML C library for Gnome</h1>
				22	<h2>Python and bindings</h2>
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				62	<table width="100%" border="0" cellspacing="1" cellpadding="3">
				63	<tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>API Indexes</b></center></td></tr>
				64	<tr><td bgcolor="#fffacd"><ul>
				65	<li><a href="APIchunk0.html">Alphabetic</a></li>
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				73	<tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Related links</b></center></td></tr>
				74	<tr><td bgcolor="#fffacd"><ul>
				75	<li><a href="http://mail.gnome.org/archives/xml/">Mail archive</a></li>
				76	<li><a href="http://xmlsoft.org/XSLT/">XSLT libxslt</a></li>
				77	<li><a href="http://phd.cs.unibo.it/gdome2/">DOM gdome2</a></li>
				78	<li><a href="ftp://xmlsoft.org/">FTP</a></li>
				79	<li><a href="http://www.fh-frankfurt.de/~igor/projects/libxml/">Windows binaries</a></li>
				80	<li><a href="http://garypennington.net/libxml2/">Solaris binaries</a></li>
				81	<li><a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml">Bug Tracker</a></li>
				82	</ul></td></tr>
				83	</table>
				84	</td></tr></table></td>
				85	<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">
				86	<p>There is a number of language bindings and wrappers available for libxml2,
				87	the list below is not exhaustive. Please contact the <a href="http://mail.gnome.org/mailman/listinfo/xml-bindings">xml-bindings@gnome.org</a>
				88	(<a href="http://mail.gnome.org/archives/xml-bindings/">archives</a>) in
				89	order to get updates to this list or to discuss the specific topic of libxml2
				90	or libxslt wrappers or bindings:</p>
				91	<ul>
				92	<li>
				93	<a href="mailto:ari@lusis.org">Ari Johnson</a>
				94	provides a C++ wrapper for libxml:<br>
				95	Website: <a href="http://lusis.org/~ari/xml++/">http://lusis.org/~ari/xml++/</a><br>
				96	Download: <a href="http://lusis.org/~ari/xml++/libxml++.tar.gz">http://lusis.org/~ari/xml++/libxml++.tar.gz</a>
				97	</li>
				98	<li>There is another <a href="http://libgdome-cpp.berlios.de/">C++ wrapper
				99	based on the gdome2 </a>bindings maintained by Tobias Peters.</li>
				100	<li>
				101	<a href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt
				102	Sergeant</a>
				103	developped <a href="http://axkit.org/download/">XML::LibXSLT</a>, a perl
				104	wrapper for libxml2/libxslt as part of the <a href="http://axkit.com/">AxKit XML application server</a>
				105	</li>
				106	<li>
				107	<a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a>
				108	provides and earlier version of the libxml/libxslt <a href="http://www.rexx.com/~dkuhlman">wrappers for Python</a>
				109	</li>
				110	<li>Petr Kozelka provides <a href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue
				111	libxml2</a> with Kylix, Delphi and other Pascal compilers</li>
				112	<li>Wai-Sun "Squidster" Chia provides <a href="http://www.rubycolor.org/arc/redist/">bindings for Ruby</a> and
				113	libxml2 bindings are also available in Ruby through the <a href="http://libgdome-ruby.berlios.de/">libgdome-ruby</a> module
				114	maintained by Tobias Peters.</li>
Daniel Veillard	b9e469a	2002-02-21 12:08:42 +0000	[diff] [blame]	115	<li>Steve Ball and contributors maintains
				116	<a href="http://tclxml.sourceforge.net/">libxml2 and libxslt bindings for
				117	Tcl</a>
				118	</li>
				119	<li>There is support for libxml2 in the DOM module of PHP.
				120	</li>
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	121	</ul>
				122	<p>The distribution includes a set of Python bindings, which are garanteed to
				123	be maintained as part of the library in the future, though the Python
Daniel Veillard	0b79dfe	2002-02-23 13:02:31 +0000	[diff] [blame]	124	interface have not yet reached the maturity of the C API.</p>
				125	<p>To install the Python bindings there are 2 options:
				126	</p>
				127	<ul>
				128	<li> If you use an RPM based distribution, simply install the
				129	<a href="http://rpmfind.net/linux/rpm2html/search.php?query=libxml2-python">libxml2-python RPM</a> (and if needed the
				130	<a href="http://rpmfind.net/linux/rpm2html/search.php?query=libxslt-python">libxslt-python RPM</a>).
				131	</li>
				132	<li> Otherwise use the <a href="ftp://xmlsoft.org/python/">libxml2-python
				133	module distribution</a> corresponding to your installed version of libxml2
				134	and libxslt. Note that to install it you will need both libxml2 and libxslt
				135	installed and run "python setup.py build install" in the module tree.
				136	</li>
				137	</ul>
				138	<p>The distribution
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	139	includes a set of examples and regression tests for the python bindings in
				140	the <code>python/tests</code> directory. Here are some excepts from those
				141	tests:</p>
				142	<h3>tst.py:</h3>
				143	<p>This is a basic test of the file interface and DOM navigation:</p>
Daniel Veillard	9eb146b	2002-02-21 16:04:51 +0000	[diff] [blame]	144	<pre>import libxml2
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	145
				146	doc = libxml2.parseFile("tst.xml")
				147	if doc.name != "tst.xml":
				148	print "doc.name failed"
				149	sys.exit(1)
				150	root = doc.children
				151	if root.name != "doc":
				152	print "root.name failed"
				153	sys.exit(1)
				154	child = root.children
				155	if child.name != "foo":
				156	print "child.name failed"
				157	sys.exit(1)
Daniel Veillard	9eb146b	2002-02-21 16:04:51 +0000	[diff] [blame]	158	doc.freeDoc()</pre>
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	159	<p>The Python module is called libxml2, parseFile is the equivalent of
				160	xmlParseFile (most of the bindings are automatically generated, and the xml
				161	prefix is removed and the casing convention are kept). All node seen at the
				162	binding level share the same subset of accesors:</p>
				163	<ul>
				164	<li>
				165	<code>name</code>
				166	: returns the node name</li>
				167	<li>
				168	<code>type</code>
				169	: returns a string indicating the node typ<code>e</code>
				170	</li>
				171	<li>
				172	<code>content</code>
				173	: returns the content of the node, it is based on xmlNodeGetContent() and
				174	hence is recursive.</li>
				175	<li>
				176	<code>parent</code>
				177	, <code>children</code>, <code>last</code>, <code>next</code>,
				178	<code>prev</code>, <code>doc</code>, <code>properties</code>: pointing to
				179	the associated element in the tree, those may return None in case no such
				180	link exists.</li>
				181	</ul>
				182	<p>Also note the need to explicitely deallocate documents with freeDoc() .
				183	Reference counting for libxml2 trees would need quite a lot of work to
				184	function properly, and rather than risk memory leaks if not implemented
				185	correctly it sounds safer to have an explicit function to free a tree. The
				186	wrapper python objects like doc, root or child are them automatically garbage
				187	collected.</p>
				188	<h3>validate.py:</h3>
				189	<p>This test check the validation interfaces and redirection of error
				190	messages:</p>
Daniel Veillard	9eb146b	2002-02-21 16:04:51 +0000	[diff] [blame]	191	<pre>import libxml2
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	192
				193	#desactivate error messages from the validation
				194	def noerr(ctx, str):
				195	pass
				196
				197	libxml2.registerErrorHandler(noerr, None)
				198
				199	ctxt = libxml2.createFileParserCtxt("invalid.xml")
				200	ctxt.validate(1)
				201	ctxt.parseDocument()
				202	doc = ctxt.doc()
				203	valid = ctxt.isValid()
				204	doc.freeDoc()
				205	if valid != 0:
Daniel Veillard	9eb146b	2002-02-21 16:04:51 +0000	[diff] [blame]	206	print "validity chec failed"</pre>
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	207	<p>The first thing to notice is the call to registerErrorHandler(), it
				208	defines a new error handler global to the library. It is used to avoid seeing
				209	the error messages when trying to validate the invalid document.</p>
				210	<p>The main interest of that test is the creation of a parser context with
				211	createFileParserCtxt() and how the behaviour can be changed before calling
				212	parseDocument() . Similary the informations resulting from the parsing phase
				213	are also available using context methods.</p>
				214	<p>Contexts like nodes are defined as class and the libxml2 wrappers maps the
				215	C function interfaces in terms of objects method as much as possible. The
				216	best to get a complete view of what methods are supported is to look at the
				217	libxml2.py module containing all the wrappers.</p>
				218	<h3>push.py:</h3>
				219	<p>This test show how to activate the push parser interface:</p>
Daniel Veillard	9eb146b	2002-02-21 16:04:51 +0000	[diff] [blame]	220	<pre>import libxml2
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	221
				222	ctxt = libxml2.createPushParser(None, "<foo", 4, "test.xml")
				223	ctxt.parseChunk("/>", 2, 1)
				224	doc = ctxt.doc()
				225
Daniel Veillard	9eb146b	2002-02-21 16:04:51 +0000	[diff] [blame]	226	doc.freeDoc()</pre>
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	227	<p>The context is created with a speciall call based on the
				228	xmlCreatePushParser() from the C library. The first argument is an optional
				229	SAX callback object, then the initial set of data, the lenght and the name of
				230	the resource in case URI-References need to be computed by the parser.</p>
				231	<p>Then the data are pushed using the parseChunk() method, the last call
				232	setting the thrird argument terminate to 1.</p>
				233	<h3>pushSAX.py:</h3>
				234	<p>this test show the use of the event based parsing interfaces. In this case
				235	the parser does not build a document, but provides callback information as
				236	the parser makes progresses analyzing the data being provided:</p>
Daniel Veillard	9eb146b	2002-02-21 16:04:51 +0000	[diff] [blame]	237	<pre>import libxml2
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	238	log = ""
				239
				240	class callback:
				241	def startDocument(self):
				242	global log
				243	log = log + "startDocument:"
				244
				245	def endDocument(self):
				246	global log
				247	log = log + "endDocument:"
				248
				249	def startElement(self, tag, attrs):
				250	global log
				251	log = log + "startElement %s %s:" % (tag, attrs)
				252
				253	def endElement(self, tag):
				254	global log
				255	log = log + "endElement %s:" % (tag)
				256
				257	def characters(self, data):
				258	global log
				259	log = log + "characters: %s:" % (data)
				260
				261	def warning(self, msg):
				262	global log
				263	log = log + "warning: %s:" % (msg)
				264
				265	def error(self, msg):
				266	global log
				267	log = log + "error: %s:" % (msg)
				268
				269	def fatalError(self, msg):
				270	global log
				271	log = log + "fatalError: %s:" % (msg)
				272
				273	handler = callback()
				274
				275	ctxt = libxml2.createPushParser(handler, "<foo", 4, "test.xml")
				276	chunk = " url='tst'>b"
				277	ctxt.parseChunk(chunk, len(chunk), 0)
				278	chunk = "ar</foo>"
				279	ctxt.parseChunk(chunk, len(chunk), 1)
				280
Daniel Veillard	fcbfa2d	2002-02-21 17:54:27 +0000	[diff] [blame]	281	reference = "startDocument:startElement foo {'url': 'tst'}:" + \
				282	"characters: bar:endElement foo:endDocument:"
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	283	if log != reference:
				284	print "Error got: %s" % log
Daniel Veillard	9eb146b	2002-02-21 16:04:51 +0000	[diff] [blame]	285	print "Exprected: %s" % reference</pre>
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	286	<p>The key object in that test is the handler, it provides a number of entry
				287	points which can be called by the parser as it makes progresses to indicate
				288	the information set obtained. The full set of callback is larger than what
				289	the callback class in that specific example implements (see the SAX
				290	definition for a complete list). The wrapper will only call those supplied by
				291	the object when activated. The startElement receives the names of the element
				292	and a dictionnary containing the attributes carried by this element.</p>
				293	<p>Also note that the reference string generated from the callback shows a
				294	single character call even though the string "bar" is passed to the parser
				295	from 2 different call to parseChunk()</p>
				296	<h3>xpath.py:</h3>
				297	<p>This is a basic test of XPath warppers support</p>
Daniel Veillard	9eb146b	2002-02-21 16:04:51 +0000	[diff] [blame]	298	<pre>import libxml2
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	299
				300	doc = libxml2.parseFile("tst.xml")
				301	ctxt = doc.xpathNewContext()
				302	res = ctxt.xpathEval("//*")
				303	if len(res) != 2:
				304	print "xpath query: wrong node set size"
				305	sys.exit(1)
				306	if res[0].name != "doc" or res[1].name != "foo":
				307	print "xpath query: wrong node set value"
				308	sys.exit(1)
				309	doc.freeDoc()
Daniel Veillard	9eb146b	2002-02-21 16:04:51 +0000	[diff] [blame]	310	ctxt.xpathFreeContext()</pre>
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	311	<p>This test parses a file, then create an XPath context to evaluate XPath
				312	expression on it. The xpathEval() method execute an XPath query and returns
				313	the result mapped in a Python way. String and numbers are natively converted,
				314	and node sets are returned as a tuple of libxml2 Python nodes wrappers. Like
				315	the document, the XPath context need to be freed explicitely, also not that
				316	the result of the XPath query may point back to the document tree and hence
				317	the document must be freed after the result of the query is used.</p>
				318	<h3>xpathext.py:</h3>
				319	<p>This test shows how to extend the XPath engine with functions written in
				320	python:</p>
Daniel Veillard	9eb146b	2002-02-21 16:04:51 +0000	[diff] [blame]	321	<pre>import libxml2
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	322
				323	def foo(ctx, x):
				324	return x + 1
				325
				326	doc = libxml2.parseFile("tst.xml")
				327	ctxt = doc.xpathNewContext()
				328	libxml2.registerXPathFunction(ctxt._o, "foo", None, foo)
				329	res = ctxt.xpathEval("foo(1)")
				330	if res != 2:
				331	print "xpath extension failure"
				332	doc.freeDoc()
Daniel Veillard	9eb146b	2002-02-21 16:04:51 +0000	[diff] [blame]	333	ctxt.xpathFreeContext()</pre>
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	334	<p>Note how the extension function is registered with the context (but that
				335	part is not yet finalized, ths may change slightly in the future).</p>
				336	<h3>tstxpath.py:</h3>
				337	<p>This test is similar to the previousone but shows how the extension
				338	function can access the XPath evaluation context:</p>
Daniel Veillard	9eb146b	2002-02-21 16:04:51 +0000	[diff] [blame]	339	<pre>def foo(ctx, x):
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	340	global called
				341
				342	#
				343	# test that access to the XPath evaluation contexts
				344	#
				345	pctxt = libxml2.xpathParserContext(_obj=ctx)
				346	ctxt = pctxt.context()
				347	called = ctxt.function()
Daniel Veillard	9eb146b	2002-02-21 16:04:51 +0000	[diff] [blame]	348	return x + 1</pre>
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	349	<p>All the interfaces around the XPath parser(or rather evaluation) context
				350	are not finalized, but it should be sufficient to do contextual work at the
				351	evaluation point.</p>
				352	<h3>Memory debugging:</h3>
				353	<p>last but not least, all tests starts with the following prologue:</p>
Daniel Veillard	9eb146b	2002-02-21 16:04:51 +0000	[diff] [blame]	354	<pre>#memory debug specific
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	355	libxml2.debugMemory(1)
Daniel Veillard	9eb146b	2002-02-21 16:04:51 +0000	[diff] [blame]	356	</pre>
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	357	<p>and ends with the following epilogue:</p>
Daniel Veillard	9eb146b	2002-02-21 16:04:51 +0000	[diff] [blame]	358	<pre>#memory debug specific
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	359	libxml2.cleanupParser()
				360	if libxml2.debugMemory(1) == 0:
				361	print "OK"
				362	else:
				363	print "Memory leak %d bytes" % (libxml2.debugMemory(1))
Daniel Veillard	9eb146b	2002-02-21 16:04:51 +0000	[diff] [blame]	364	libxml2.dumpMemory()</pre>
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	365	<p>Those activate the memory debugging interface of libxml2 where all
				366	alloacted block in the library are tracked. The prologue then cleans up the
				367	library state and checks that all allocated memory has been freed. If not it
				368	calls dumpMemory() which saves that list in a <code>.memdump</code> file.</p>
				369	<p><a href="bugs.html">Daniel Veillard</a></p>
				370	</td></tr></table></td></tr></table></td></tr></table></td>
				371	</tr></table></td></tr></table>
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