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22<h1>The XML C library for Gnome</h1>
23<h2>Python and bindings</h2>
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74<tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Related links</b></center></td></tr>
75<tr><td bgcolor="#fffacd"><ul>
76<li><a href="http://mail.gnome.org/archives/xml/">Mail archive</a></li>
77<li><a href="http://xmlsoft.org/XSLT/">XSLT libxslt</a></li>
78<li><a href="http://phd.cs.unibo.it/gdome2/">DOM gdome2</a></li>
79<li><a href="ftp://xmlsoft.org/">FTP</a></li>
80<li><a href="http://www.fh-frankfurt.de/~igor/projects/libxml/">Windows binaries</a></li>
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87<p>There is a number of language bindings and wrappers available for libxml2,
88the list below is not exhaustive. Please contact the <a href="http://mail.gnome.org/mailman/listinfo/xml-bindings">xml-bindings@gnome.org</a>
89(<a href="http://mail.gnome.org/archives/xml-bindings/">archives</a>) in
90order to get updates to this list or to discuss the specific topic of libxml2
91or libxslt wrappers or bindings:</p>
92<ul>
93<li>
94<a href="mailto:ari@lusis.org">Ari Johnson</a>
95 provides a C++ wrapper for libxml:<br>
96 Website: <a href="http://lusis.org/~ari/xml++/">http://lusis.org/~ari/xml++/</a><br>
97 Download: <a href="http://lusis.org/~ari/xml++/libxml++.tar.gz">http://lusis.org/~ari/xml++/libxml++.tar.gz</a>
98</li>
99<li>There is another <a href="http://libgdome-cpp.berlios.de/">C++ wrapper
100 based on the gdome2 </a>bindings maintained by Tobias Peters.</li>
101<li>
102<a href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt
103 Sergeant</a>
104 developped <a href="http://axkit.org/download/">XML::LibXSLT</a>, a perl
105 wrapper for libxml2/libxslt as part of the <a href="http://axkit.com/">AxKit XML application server</a>
106</li>
107<li>
108<a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a>
109 provides and earlier version of the libxml/libxslt <a href="http://www.rexx.com/~dkuhlman">wrappers for Python</a>
110</li>
111<li>Petr Kozelka provides <a href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue
112 libxml2</a> with Kylix, Delphi and other Pascal compilers</li>
113<li>Wai-Sun &quot;Squidster&quot; Chia provides <a href="http://www.rubycolor.org/arc/redist/">bindings for Ruby</a> and
114 libxml2 bindings are also available in Ruby through the <a href="http://libgdome-ruby.berlios.de/">libgdome-ruby</a> module
115 maintained by Tobias Peters.</li>
Daniel Veillardb9e469a2002-02-21 12:08:42 +0000[diff] [blame]116<li>Steve Ball and contributors maintains
117 <a href="http://tclxml.sourceforge.net/">libxml2 and libxslt bindings for
118 Tcl</a>
119</li>
120<li>There is support for libxml2 in the DOM module of PHP.
121</li>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]122</ul>
123<p>The distribution includes a set of Python bindings, which are garanteed to
124be maintained as part of the library in the future, though the Python
125interface have not yet reached the maturity of the C API. The distribution
126includes a set of examples and regression tests for the python bindings in
127the <code>python/tests</code> directory. Here are some excepts from those
128tests:</p>
129<h3>tst.py:</h3>
130<p>This is a basic test of the file interface and DOM navigation:</p>
Daniel Veillard373a4752002-02-21 14:46:29 +0000[diff] [blame^]131<code>import libxml2
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]132
133doc = libxml2.parseFile(&quot;tst.xml&quot;)
134if doc.name != &quot;tst.xml&quot;:
135 print &quot;doc.name failed&quot;
136 sys.exit(1)
137root = doc.children
138if root.name != &quot;doc&quot;:
139 print &quot;root.name failed&quot;
140 sys.exit(1)
141child = root.children
142if child.name != &quot;foo&quot;:
143 print &quot;child.name failed&quot;
144 sys.exit(1)
Daniel Veillard373a4752002-02-21 14:46:29 +0000[diff] [blame^]145doc.freeDoc()</code>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]146<p>The Python module is called libxml2, parseFile is the equivalent of
147xmlParseFile (most of the bindings are automatically generated, and the xml
148prefix is removed and the casing convention are kept). All node seen at the
149binding level share the same subset of accesors:</p>
150<ul>
151<li>
152<code>name</code>
153 : returns the node name</li>
154<li>
155<code>type</code>
156 : returns a string indicating the node typ<code>e</code>
157</li>
158<li>
159<code>content</code>
160 : returns the content of the node, it is based on xmlNodeGetContent() and
161 hence is recursive.</li>
162<li>
163<code>parent</code>
164 , <code>children</code>, <code>last</code>, <code>next</code>,
165 <code>prev</code>, <code>doc</code>, <code>properties</code>: pointing to
166 the associated element in the tree, those may return None in case no such
167 link exists.</li>
168</ul>
169<p>Also note the need to explicitely deallocate documents with freeDoc() .
170Reference counting for libxml2 trees would need quite a lot of work to
171function properly, and rather than risk memory leaks if not implemented
172correctly it sounds safer to have an explicit function to free a tree. The
173wrapper python objects like doc, root or child are them automatically garbage
174collected.</p>
175<h3>validate.py:</h3>
176<p>This test check the validation interfaces and redirection of error
177messages:</p>
Daniel Veillard373a4752002-02-21 14:46:29 +0000[diff] [blame^]178<code>import libxml2
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]179
180#desactivate error messages from the validation
181def noerr(ctx, str):
182 pass
183
184libxml2.registerErrorHandler(noerr, None)
185
186ctxt = libxml2.createFileParserCtxt(&quot;invalid.xml&quot;)
187ctxt.validate(1)
188ctxt.parseDocument()
189doc = ctxt.doc()
190valid = ctxt.isValid()
191doc.freeDoc()
192if valid != 0:
Daniel Veillard373a4752002-02-21 14:46:29 +0000[diff] [blame^]193 print &quot;validity chec failed&quot;</code>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]194<p>The first thing to notice is the call to registerErrorHandler(), it
195defines a new error handler global to the library. It is used to avoid seeing
196the error messages when trying to validate the invalid document.</p>
197<p>The main interest of that test is the creation of a parser context with
198createFileParserCtxt() and how the behaviour can be changed before calling
199parseDocument() . Similary the informations resulting from the parsing phase
200are also available using context methods.</p>
201<p>Contexts like nodes are defined as class and the libxml2 wrappers maps the
202C function interfaces in terms of objects method as much as possible. The
203best to get a complete view of what methods are supported is to look at the
204libxml2.py module containing all the wrappers.</p>
205<h3>push.py:</h3>
206<p>This test show how to activate the push parser interface:</p>
Daniel Veillard373a4752002-02-21 14:46:29 +0000[diff] [blame^]207<code>import libxml2
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]208
209ctxt = libxml2.createPushParser(None, &quot;&lt;foo&quot;, 4, &quot;test.xml&quot;)
210ctxt.parseChunk(&quot;/&gt;&quot;, 2, 1)
211doc = ctxt.doc()
212
Daniel Veillard373a4752002-02-21 14:46:29 +0000[diff] [blame^]213doc.freeDoc()</code>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]214<p>The context is created with a speciall call based on the
215xmlCreatePushParser() from the C library. The first argument is an optional
216SAX callback object, then the initial set of data, the lenght and the name of
217the resource in case URI-References need to be computed by the parser.</p>
218<p>Then the data are pushed using the parseChunk() method, the last call
219setting the thrird argument terminate to 1.</p>
220<h3>pushSAX.py:</h3>
221<p>this test show the use of the event based parsing interfaces. In this case
222the parser does not build a document, but provides callback information as
223the parser makes progresses analyzing the data being provided:</p>
Daniel Veillard373a4752002-02-21 14:46:29 +0000[diff] [blame^]224<code>import libxml2
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]225log = &quot;&quot;
226
227class callback:
228 def startDocument(self):
229 global log
230 log = log + &quot;startDocument:&quot;
231
232 def endDocument(self):
233 global log
234 log = log + &quot;endDocument:&quot;
235
236 def startElement(self, tag, attrs):
237 global log
238 log = log + &quot;startElement %s %s:&quot; % (tag, attrs)
239
240 def endElement(self, tag):
241 global log
242 log = log + &quot;endElement %s:&quot; % (tag)
243
244 def characters(self, data):
245 global log
246 log = log + &quot;characters: %s:&quot; % (data)
247
248 def warning(self, msg):
249 global log
250 log = log + &quot;warning: %s:&quot; % (msg)
251
252 def error(self, msg):
253 global log
254 log = log + &quot;error: %s:&quot; % (msg)
255
256 def fatalError(self, msg):
257 global log
258 log = log + &quot;fatalError: %s:&quot; % (msg)
259
260handler = callback()
261
262ctxt = libxml2.createPushParser(handler, &quot;&lt;foo&quot;, 4, &quot;test.xml&quot;)
263chunk = &quot; url='tst'&gt;b&quot;
264ctxt.parseChunk(chunk, len(chunk), 0)
265chunk = &quot;ar&lt;/foo&gt;&quot;
266ctxt.parseChunk(chunk, len(chunk), 1)
267
268reference = &quot;startDocument:startElement foo {'url': 'tst'}:characters: bar:endElement foo:endDocument:&quot;
269if log != reference:
270 print &quot;Error got: %s&quot; % log
Daniel Veillard373a4752002-02-21 14:46:29 +0000[diff] [blame^]271 print &quot;Exprected: %s&quot; % reference</code>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]272<p>The key object in that test is the handler, it provides a number of entry
273points which can be called by the parser as it makes progresses to indicate
274the information set obtained. The full set of callback is larger than what
275the callback class in that specific example implements (see the SAX
276definition for a complete list). The wrapper will only call those supplied by
277the object when activated. The startElement receives the names of the element
278and a dictionnary containing the attributes carried by this element.</p>
279<p>Also note that the reference string generated from the callback shows a
280single character call even though the string &quot;bar&quot; is passed to the parser
281from 2 different call to parseChunk()</p>
282<h3>xpath.py:</h3>
283<p>This is a basic test of XPath warppers support</p>
Daniel Veillard373a4752002-02-21 14:46:29 +0000[diff] [blame^]284<code>import libxml2
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]285
286doc = libxml2.parseFile(&quot;tst.xml&quot;)
287ctxt = doc.xpathNewContext()
288res = ctxt.xpathEval(&quot;//*&quot;)
289if len(res) != 2:
290 print &quot;xpath query: wrong node set size&quot;
291 sys.exit(1)
292if res[0].name != &quot;doc&quot; or res[1].name != &quot;foo&quot;:
293 print &quot;xpath query: wrong node set value&quot;
294 sys.exit(1)
295doc.freeDoc()
Daniel Veillard373a4752002-02-21 14:46:29 +0000[diff] [blame^]296ctxt.xpathFreeContext()</code>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]297<p>This test parses a file, then create an XPath context to evaluate XPath
298expression on it. The xpathEval() method execute an XPath query and returns
299the result mapped in a Python way. String and numbers are natively converted,
300and node sets are returned as a tuple of libxml2 Python nodes wrappers. Like
301the document, the XPath context need to be freed explicitely, also not that
302the result of the XPath query may point back to the document tree and hence
303the document must be freed after the result of the query is used.</p>
304<h3>xpathext.py:</h3>
305<p>This test shows how to extend the XPath engine with functions written in
306python:</p>
Daniel Veillard373a4752002-02-21 14:46:29 +0000[diff] [blame^]307<code>import libxml2
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]308
309def foo(ctx, x):
310 return x + 1
311
312doc = libxml2.parseFile(&quot;tst.xml&quot;)
313ctxt = doc.xpathNewContext()
314libxml2.registerXPathFunction(ctxt._o, &quot;foo&quot;, None, foo)
315res = ctxt.xpathEval(&quot;foo(1)&quot;)
316if res != 2:
317 print &quot;xpath extension failure&quot;
318doc.freeDoc()
Daniel Veillard373a4752002-02-21 14:46:29 +0000[diff] [blame^]319ctxt.xpathFreeContext()</code>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]320<p>Note how the extension function is registered with the context (but that
321part is not yet finalized, ths may change slightly in the future).</p>
322<h3>tstxpath.py:</h3>
323<p>This test is similar to the previousone but shows how the extension
324function can access the XPath evaluation context:</p>
Daniel Veillard373a4752002-02-21 14:46:29 +0000[diff] [blame^]325<code>def foo(ctx, x):
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]326 global called
327
328 #
329 # test that access to the XPath evaluation contexts
330 #
331 pctxt = libxml2.xpathParserContext(_obj=ctx)
332 ctxt = pctxt.context()
333 called = ctxt.function()
Daniel Veillard373a4752002-02-21 14:46:29 +0000[diff] [blame^]334 return x + 1</code>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]335<p>All the interfaces around the XPath parser(or rather evaluation) context
336are not finalized, but it should be sufficient to do contextual work at the
337evaluation point.</p>
338<h3>Memory debugging:</h3>
339<p>last but not least, all tests starts with the following prologue:</p>
Daniel Veillard373a4752002-02-21 14:46:29 +0000[diff] [blame^]340<code>#memory debug specific
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]341libxml2.debugMemory(1)
Daniel Veillard373a4752002-02-21 14:46:29 +0000[diff] [blame^]342</code>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]343<p>and ends with the following epilogue:</p>
Daniel Veillard373a4752002-02-21 14:46:29 +0000[diff] [blame^]344<code>#memory debug specific
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]345libxml2.cleanupParser()
346if libxml2.debugMemory(1) == 0:
347 print &quot;OK&quot;
348else:
349 print &quot;Memory leak %d bytes&quot; % (libxml2.debugMemory(1))
Daniel Veillard373a4752002-02-21 14:46:29 +0000[diff] [blame^]350 libxml2.dumpMemory()</code>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]351<p>Those activate the memory debugging interface of libxml2 where all
352alloacted block in the library are tracked. The prologue then cleans up the
353library state and checks that all allocated memory has been freed. If not it
354calls dumpMemory() which saves that list in a <code>.memdump</code> file.</p>
355<p><a href="bugs.html">Daniel Veillard</a></p>
356</td></tr></table></td></tr></table></td></tr></table></td>
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