Gitiles
Code Review Sign In
gerrit-public.fairphone.software / platform / external / libxml2 / 21473679f7ada2f947e93065eb26c67970695c46 / . / doc / python.html
blob: 77970815ba9e14c096161261cef897e4a90a48d8 [file] [log] [blame]
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/1999/REC-html401-19991224/loose.dtd">
2<html>
3<head>
4<meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type">
Daniel Veillardc332dab2002-03-29 14:08:27 +0000[diff] [blame]5<link rel="SHORTCUT ICON" href="/favicon.ico">
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]6<style type="text/css"><!--
Daniel Veillard373a4752002-02-21 14:46:29 +0000[diff] [blame]7TD {font-family: Verdana,Arial,Helvetica}
8BODY {font-family: Verdana,Arial,Helvetica; margin-top: 2em; margin-left: 0em; margin-right: 0em}
9H1 {font-family: Verdana,Arial,Helvetica}
10H2 {font-family: Verdana,Arial,Helvetica}
11H3 {font-family: Verdana,Arial,Helvetica}
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]12A:link, A:visited, A:active { text-decoration: underline }
13--></style>
14<title>Python and bindings</title>
15</head>
16<body bgcolor="#8b7765" text="#000000" link="#000000" vlink="#000000">
17<table border="0" width="100%" cellpadding="5" cellspacing="0" align="center"><tr>
18<td width="180">
19<a href="http://www.gnome.org/"><img src="smallfootonly.gif" alt="Gnome 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>
20</td>
21<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">
22<h1>The XML C library for Gnome</h1>
23<h2>Python and bindings</h2>
24</td></tr></table></td></tr></table></td>
25</tr></table>
26<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>
27<td valign="top" width="200" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td>
28<table width="100%" border="0" cellspacing="1" cellpadding="3">
29<tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Main Menu</b></center></td></tr>
30<tr><td bgcolor="#fffacd"><ul>
31<li><a href="index.html">Home</a></li>
32<li><a href="intro.html">Introduction</a></li>
33<li><a href="FAQ.html">FAQ</a></li>
34<li><a href="docs.html">Documentation</a></li>
35<li><a href="bugs.html">Reporting bugs and getting help</a></li>
36<li><a href="help.html">How to help</a></li>
37<li><a href="downloads.html">Downloads</a></li>
38<li><a href="news.html">News</a></li>
39<li><a href="XMLinfo.html">XML</a></li>
40<li><a href="XSLT.html">XSLT</a></li>
41<li><a href="python.html">Python and bindings</a></li>
42<li><a href="architecture.html">libxml architecture</a></li>
43<li><a href="tree.html">The tree output</a></li>
44<li><a href="interface.html">The SAX interface</a></li>
45<li><a href="xmldtd.html">Validation &amp; DTDs</a></li>
46<li><a href="xmlmem.html">Memory Management</a></li>
47<li><a href="encoding.html">Encodings support</a></li>
48<li><a href="xmlio.html">I/O Interfaces</a></li>
49<li><a href="catalog.html">Catalog support</a></li>
50<li><a href="library.html">The parser interfaces</a></li>
51<li><a href="entities.html">Entities or no entities</a></li>
52<li><a href="namespaces.html">Namespaces</a></li>
53<li><a href="upgrade.html">Upgrading 1.x code</a></li>
54<li><a href="threads.html">Thread safety</a></li>
55<li><a href="DOM.html">DOM Principles</a></li>
56<li><a href="example.html">A real example</a></li>
57<li><a href="contribs.html">Contributions</a></li>
Daniel Veillardfc59c092002-06-05 14:48:26 +0000[diff] [blame]58<li><a href="tutorial/index.html">Tutorial</a></li>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]59<li>
60<a href="xml.html">flat page</a>, <a href="site.xsl">stylesheet</a>
61</li>
62</ul></td></tr>
63</table>
64<table width="100%" border="0" cellspacing="1" cellpadding="3">
65<tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>API Indexes</b></center></td></tr>
66<tr><td bgcolor="#fffacd"><ul>
67<li><a href="APIchunk0.html">Alphabetic</a></li>
68<li><a href="APIconstructors.html">Constructors</a></li>
69<li><a href="APIfunctions.html">Functions/Types</a></li>
70<li><a href="APIfiles.html">Modules</a></li>
71<li><a href="APIsymbols.html">Symbols</a></li>
72</ul></td></tr>
73</table>
74<table width="100%" border="0" cellspacing="1" cellpadding="3">
75<tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Related links</b></center></td></tr>
76<tr><td bgcolor="#fffacd"><ul>
77<li><a href="http://mail.gnome.org/archives/xml/">Mail archive</a></li>
78<li><a href="http://xmlsoft.org/XSLT/">XSLT libxslt</a></li>
79<li><a href="http://phd.cs.unibo.it/gdome2/">DOM gdome2</a></li>
Daniel Veillard2d347fa2002-03-17 10:34:11 +0000[diff] [blame]80<li><a href="http://www.aleksey.com/xmlsec/">XML-DSig xmlsec</a></li>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]81<li><a href="ftp://xmlsoft.org/">FTP</a></li>
82<li><a href="http://www.fh-frankfurt.de/~igor/projects/libxml/">Windows binaries</a></li>
83<li><a href="http://garypennington.net/libxml2/">Solaris binaries</a></li>
Daniel Veillarde6d8e202002-05-02 06:11:10 +0000[diff] [blame]84<li><a href="http://sourceforge.net/projects/libxml2-pas/">Pascal bindings</a></li>
Daniel Veillard2d347fa2002-03-17 10:34:11 +0000[diff] [blame]85<li><a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml&amp;product=libxml2">Bug Tracker</a></li>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]86</ul></td></tr>
87</table>
88</td></tr></table></td>
89<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">
90<p>There is a number of language bindings and wrappers available for libxml2,
91the list below is not exhaustive. Please contact the <a href="http://mail.gnome.org/mailman/listinfo/xml-bindings">xml-bindings@gnome.org</a>
92(<a href="http://mail.gnome.org/archives/xml-bindings/">archives</a>) in
93order to get updates to this list or to discuss the specific topic of libxml2
94or libxslt wrappers or bindings:</p>
95<ul>
96<li>
Daniel Veillardaf43f632002-03-08 15:05:20 +0000[diff] [blame]97<a href="mailto:ari@lusis.org">Ari Johnson</a> provides a C++ wrapper
98 for libxml:<br>
Daniel Veillard9b6fd302002-05-13 12:06:47 +0000[diff] [blame]99 Website: <a href="http://lusis.org/~ari/xml%2B%2B/">http://lusis.org/~ari/xml++/</a><br>
100 Download: <a href="http://lusis.org/~ari/xml%2B%2B/libxml%2B%2B.tar.gz">http://lusis.org/~ari/xml++/libxml++.tar.gz</a>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]101</li>
102<li>There is another <a href="http://libgdome-cpp.berlios.de/">C++ wrapper
103 based on the gdome2 </a>bindings maintained by Tobias Peters.</li>
Daniel Veillard9b6fd302002-05-13 12:06:47 +0000[diff] [blame]104<li>and a third C++ wrapper by Peter Jones &lt;pjones@pmade.org&gt;
105 <p>Website: <a href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a>
106</p>
107</li>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]108<li>
109<a href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt
Daniel Veillard63d83142002-05-20 06:51:05 +0000[diff] [blame]110 Sergeant</a> developed <a href="http://axkit.org/download/">XML::LibXSLT</a>, a Perl wrapper for
Daniel Veillardaf43f632002-03-08 15:05:20 +0000[diff] [blame]111 libxml2/libxslt as part of the <a href="http://axkit.com/">AxKit XML
112 application server</a>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]113</li>
114<li>
Daniel Veillard21473672002-06-17 07:29:22 +0000[diff] [blame^]115<a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a> provides an
Daniel Veillardaf43f632002-03-08 15:05:20 +0000[diff] [blame]116 earlier version of the libxml/libxslt <a href="http://www.rexx.com/~dkuhlman">wrappers for Python</a>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]117</li>
Daniel Veillard21473672002-06-17 07:29:22 +0000[diff] [blame^]118<li>Gopal.V and Peter Minten develop <a href="http://savannah.gnu.org/projects/libxmlsharp">libxml#</a>, a set of
119 C# libxml2 bindings</li>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]120<li>Petr Kozelka provides <a href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue
121 libxml2</a> with Kylix, Delphi and other Pascal compilers</li>
Daniel Veillardb2fb8ed2002-04-01 09:33:12 +0000[diff] [blame]122<li>Uwe Fechner also provides <a href="http://sourceforge.net/projects/idom2-pas/">idom2</a>, a DOM2
Daniel Veillarda8a89fe2002-04-12 21:03:34 +0000[diff] [blame]123 implementation for Kylix2/D5/D6 from Borland</li>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]124<li>Wai-Sun &quot;Squidster&quot; Chia provides <a href="http://www.rubycolor.org/arc/redist/">bindings for Ruby</a> and
125 libxml2 bindings are also available in Ruby through the <a href="http://libgdome-ruby.berlios.de/">libgdome-ruby</a> module
126 maintained by Tobias Peters.</li>
Daniel Veillardaf43f632002-03-08 15:05:20 +0000[diff] [blame]127<li>Steve Ball and contributors maintains <a href="http://tclxml.sourceforge.net/">libxml2 and libxslt bindings for
Daniel Veillardb9e469a2002-02-21 12:08:42 +0000[diff] [blame]128 Tcl</a>
129</li>
Daniel Veillardaf43f632002-03-08 15:05:20 +0000[diff] [blame]130<li>There is support for libxml2 in the DOM module of PHP.</li>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]131</ul>
Daniel Veillardc0801af2002-05-28 16:28:42 +0000[diff] [blame]132<p>The distribution includes a set of Python bindings, which are guaranteed
133to be maintained as part of the library in the future, though the Python
Daniel Veillard0b79dfe2002-02-23 13:02:31 +0000[diff] [blame]134interface have not yet reached the maturity of the C API.</p>
Daniel Veillardaf43f632002-03-08 15:05:20 +0000[diff] [blame]135<p>To install the Python bindings there are 2 options:</p>
Daniel Veillard0b79dfe2002-02-23 13:02:31 +0000[diff] [blame]136<ul>
Daniel Veillardaf43f632002-03-08 15:05:20 +0000[diff] [blame]137<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
138 RPM</a> (and if needed the <a href="http://rpmfind.net/linux/rpm2html/search.php?query=libxslt-python">libxslt-python
139 RPM</a>).</li>
140<li>Otherwise use the <a href="ftp://xmlsoft.org/python/">libxml2-python
141 module distribution</a> corresponding to your installed version of
142 libxml2 and libxslt. Note that to install it you will need both libxml2
143 and libxslt installed and run &quot;python setup.py build install&quot; in the
144 module tree.</li>
Daniel Veillard0b79dfe2002-02-23 13:02:31 +0000[diff] [blame]145</ul>
Daniel Veillardaf43f632002-03-08 15:05:20 +0000[diff] [blame]146<p>The distribution includes a set of examples and regression tests for the
147python bindings in the <code>python/tests</code> directory. Here are some
148excepts from those tests:</p>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]149<h3>tst.py:</h3>
150<p>This is a basic test of the file interface and DOM navigation:</p>
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]151<pre>import libxml2
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]152
153doc = libxml2.parseFile(&quot;tst.xml&quot;)
154if doc.name != &quot;tst.xml&quot;:
155 print &quot;doc.name failed&quot;
156 sys.exit(1)
157root = doc.children
158if root.name != &quot;doc&quot;:
159 print &quot;root.name failed&quot;
160 sys.exit(1)
161child = root.children
162if child.name != &quot;foo&quot;:
163 print &quot;child.name failed&quot;
164 sys.exit(1)
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]165doc.freeDoc()</pre>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]166<p>The Python module is called libxml2, parseFile is the equivalent of
167xmlParseFile (most of the bindings are automatically generated, and the xml
168prefix is removed and the casing convention are kept). All node seen at the
Daniel Veillard63d83142002-05-20 06:51:05 +0000[diff] [blame]169binding level share the same subset of accessors:</p>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]170<ul>
171<li>
Daniel Veillardaf43f632002-03-08 15:05:20 +0000[diff] [blame]172<code>name</code> : returns the node name</li>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]173<li>
Daniel Veillardc0801af2002-05-28 16:28:42 +0000[diff] [blame]174<code>type</code> : returns a string indicating the node type</li>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]175<li>
Daniel Veillardaf43f632002-03-08 15:05:20 +0000[diff] [blame]176<code>content</code> : returns the content of the node, it is based on
177 xmlNodeGetContent() and hence is recursive.</li>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]178<li>
Daniel Veillardaf43f632002-03-08 15:05:20 +0000[diff] [blame]179<code>parent</code> , <code>children</code>, <code>last</code>,
180 <code>next</code>, <code>prev</code>, <code>doc</code>,
181 <code>properties</code>: pointing to the associated element in the tree,
182 those may return None in case no such link exists.</li>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]183</ul>
Daniel Veillard63d83142002-05-20 06:51:05 +0000[diff] [blame]184<p>Also note the need to explicitly deallocate documents with freeDoc() .
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]185Reference counting for libxml2 trees would need quite a lot of work to
186function properly, and rather than risk memory leaks if not implemented
187correctly it sounds safer to have an explicit function to free a tree. The
188wrapper python objects like doc, root or child are them automatically garbage
189collected.</p>
190<h3>validate.py:</h3>
191<p>This test check the validation interfaces and redirection of error
192messages:</p>
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]193<pre>import libxml2
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]194
Daniel Veillard63d83142002-05-20 06:51:05 +0000[diff] [blame]195#deactivate error messages from the validation
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]196def noerr(ctx, str):
197 pass
198
199libxml2.registerErrorHandler(noerr, None)
200
201ctxt = libxml2.createFileParserCtxt(&quot;invalid.xml&quot;)
202ctxt.validate(1)
203ctxt.parseDocument()
204doc = ctxt.doc()
205valid = ctxt.isValid()
206doc.freeDoc()
207if valid != 0:
Daniel Veillard63d83142002-05-20 06:51:05 +0000[diff] [blame]208 print &quot;validity check failed&quot;</pre>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]209<p>The first thing to notice is the call to registerErrorHandler(), it
210defines a new error handler global to the library. It is used to avoid seeing
211the error messages when trying to validate the invalid document.</p>
212<p>The main interest of that test is the creation of a parser context with
213createFileParserCtxt() and how the behaviour can be changed before calling
Daniel Veillard63d83142002-05-20 06:51:05 +0000[diff] [blame]214parseDocument() . Similarly the informations resulting from the parsing phase
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]215are also available using context methods.</p>
216<p>Contexts like nodes are defined as class and the libxml2 wrappers maps the
217C function interfaces in terms of objects method as much as possible. The
218best to get a complete view of what methods are supported is to look at the
219libxml2.py module containing all the wrappers.</p>
220<h3>push.py:</h3>
221<p>This test show how to activate the push parser interface:</p>
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]222<pre>import libxml2
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]223
224ctxt = libxml2.createPushParser(None, &quot;&lt;foo&quot;, 4, &quot;test.xml&quot;)
225ctxt.parseChunk(&quot;/&gt;&quot;, 2, 1)
226doc = ctxt.doc()
227
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]228doc.freeDoc()</pre>
Daniel Veillard63d83142002-05-20 06:51:05 +0000[diff] [blame]229<p>The context is created with a special call based on the
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]230xmlCreatePushParser() from the C library. The first argument is an optional
Daniel Veillard63d83142002-05-20 06:51:05 +0000[diff] [blame]231SAX callback object, then the initial set of data, the length and the name of
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]232the resource in case URI-References need to be computed by the parser.</p>
233<p>Then the data are pushed using the parseChunk() method, the last call
Daniel Veillard63d83142002-05-20 06:51:05 +0000[diff] [blame]234setting the third argument terminate to 1.</p>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]235<h3>pushSAX.py:</h3>
236<p>this test show the use of the event based parsing interfaces. In this case
237the parser does not build a document, but provides callback information as
238the parser makes progresses analyzing the data being provided:</p>
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]239<pre>import libxml2
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]240log = &quot;&quot;
241
242class callback:
243 def startDocument(self):
244 global log
245 log = log + &quot;startDocument:&quot;
246
247 def endDocument(self):
248 global log
249 log = log + &quot;endDocument:&quot;
250
251 def startElement(self, tag, attrs):
252 global log
253 log = log + &quot;startElement %s %s:&quot; % (tag, attrs)
254
255 def endElement(self, tag):
256 global log
257 log = log + &quot;endElement %s:&quot; % (tag)
258
259 def characters(self, data):
260 global log
261 log = log + &quot;characters: %s:&quot; % (data)
262
263 def warning(self, msg):
264 global log
265 log = log + &quot;warning: %s:&quot; % (msg)
266
267 def error(self, msg):
268 global log
269 log = log + &quot;error: %s:&quot; % (msg)
270
271 def fatalError(self, msg):
272 global log
273 log = log + &quot;fatalError: %s:&quot; % (msg)
274
275handler = callback()
276
277ctxt = libxml2.createPushParser(handler, &quot;&lt;foo&quot;, 4, &quot;test.xml&quot;)
278chunk = &quot; url='tst'&gt;b&quot;
279ctxt.parseChunk(chunk, len(chunk), 0)
280chunk = &quot;ar&lt;/foo&gt;&quot;
281ctxt.parseChunk(chunk, len(chunk), 1)
282
Daniel Veillardfcbfa2d2002-02-21 17:54:27 +0000[diff] [blame]283reference = &quot;startDocument:startElement foo {'url': 'tst'}:&quot; + \
284 &quot;characters: bar:endElement foo:endDocument:&quot;
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]285if log != reference:
286 print &quot;Error got: %s&quot; % log
Daniel Veillard63d83142002-05-20 06:51:05 +0000[diff] [blame]287 print &quot;Expected: %s&quot; % reference</pre>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]288<p>The key object in that test is the handler, it provides a number of entry
289points which can be called by the parser as it makes progresses to indicate
290the information set obtained. The full set of callback is larger than what
291the callback class in that specific example implements (see the SAX
292definition for a complete list). The wrapper will only call those supplied by
293the object when activated. The startElement receives the names of the element
Daniel Veillard63d83142002-05-20 06:51:05 +0000[diff] [blame]294and a dictionary containing the attributes carried by this element.</p>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]295<p>Also note that the reference string generated from the callback shows a
296single character call even though the string &quot;bar&quot; is passed to the parser
297from 2 different call to parseChunk()</p>
298<h3>xpath.py:</h3>
Daniel Veillard63d83142002-05-20 06:51:05 +0000[diff] [blame]299<p>This is a basic test of XPath wrappers support</p>
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]300<pre>import libxml2
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]301
302doc = libxml2.parseFile(&quot;tst.xml&quot;)
303ctxt = doc.xpathNewContext()
304res = ctxt.xpathEval(&quot;//*&quot;)
305if len(res) != 2:
306 print &quot;xpath query: wrong node set size&quot;
307 sys.exit(1)
308if res[0].name != &quot;doc&quot; or res[1].name != &quot;foo&quot;:
309 print &quot;xpath query: wrong node set value&quot;
310 sys.exit(1)
311doc.freeDoc()
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]312ctxt.xpathFreeContext()</pre>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]313<p>This test parses a file, then create an XPath context to evaluate XPath
314expression on it. The xpathEval() method execute an XPath query and returns
315the result mapped in a Python way. String and numbers are natively converted,
316and node sets are returned as a tuple of libxml2 Python nodes wrappers. Like
Daniel Veillard63d83142002-05-20 06:51:05 +0000[diff] [blame]317the document, the XPath context need to be freed explicitly, also not that
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]318the result of the XPath query may point back to the document tree and hence
319the document must be freed after the result of the query is used.</p>
320<h3>xpathext.py:</h3>
321<p>This test shows how to extend the XPath engine with functions written in
322python:</p>
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]323<pre>import libxml2
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]324
325def foo(ctx, x):
326 return x + 1
327
328doc = libxml2.parseFile(&quot;tst.xml&quot;)
329ctxt = doc.xpathNewContext()
330libxml2.registerXPathFunction(ctxt._o, &quot;foo&quot;, None, foo)
331res = ctxt.xpathEval(&quot;foo(1)&quot;)
332if res != 2:
333 print &quot;xpath extension failure&quot;
334doc.freeDoc()
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]335ctxt.xpathFreeContext()</pre>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]336<p>Note how the extension function is registered with the context (but that
Daniel Veillard63d83142002-05-20 06:51:05 +0000[diff] [blame]337part is not yet finalized, this may change slightly in the future).</p>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]338<h3>tstxpath.py:</h3>
Daniel Veillard63d83142002-05-20 06:51:05 +0000[diff] [blame]339<p>This test is similar to the previous one but shows how the extension
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]340function can access the XPath evaluation context:</p>
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]341<pre>def foo(ctx, x):
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]342 global called
343
344 #
345 # test that access to the XPath evaluation contexts
346 #
347 pctxt = libxml2.xpathParserContext(_obj=ctx)
348 ctxt = pctxt.context()
349 called = ctxt.function()
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]350 return x + 1</pre>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]351<p>All the interfaces around the XPath parser(or rather evaluation) context
352are not finalized, but it should be sufficient to do contextual work at the
353evaluation point.</p>
354<h3>Memory debugging:</h3>
355<p>last but not least, all tests starts with the following prologue:</p>
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]356<pre>#memory debug specific
Daniel Veillardaf43f632002-03-08 15:05:20 +0000[diff] [blame]357libxml2.debugMemory(1)</pre>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]358<p>and ends with the following epilogue:</p>
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]359<pre>#memory debug specific
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]360libxml2.cleanupParser()
361if libxml2.debugMemory(1) == 0:
362 print &quot;OK&quot;
363else:
364 print &quot;Memory leak %d bytes&quot; % (libxml2.debugMemory(1))
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]365 libxml2.dumpMemory()</pre>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]366<p>Those activate the memory debugging interface of libxml2 where all
Daniel Veillard63d83142002-05-20 06:51:05 +0000[diff] [blame]367allocated block in the library are tracked. The prologue then cleans up the
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]368library state and checks that all allocated memory has been freed. If not it
369calls dumpMemory() which saves that list in a <code>.memdump</code> file.</p>
370<p><a href="bugs.html">Daniel Veillard</a></p>
371</td></tr></table></td></tr></table></td></tr></table></td>
372</tr></table></td></tr></table>
373</body>
374</html>