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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 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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://www.blastwave.org/packages.php/libxml2">Solaris binaries</a></li><li><a href="http://www.explain.com.au/oss/libxml2xslt.html">MacOsX binaries</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://rubyforge.org/projects/xml-tools/">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
11libxml2, 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
13order to get updates to this list or to discuss the specific topic of libxml2
14or libxslt wrappers or bindings:</p><ul><li><a href="http://libxmlplusplus.sourceforge.net/">Libxml++</a> seems the
15    most up-to-date C++ bindings for libxml2, check the <a href="http://libxmlplusplus.sourceforge.net/reference/html/hierarchy.html">documentation</a>
16    and the <a href="http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/libxmlplusplus/libxml%2b%2b/examples/">examples</a>.</li>
17  <li>There is another <a href="http://libgdome-cpp.berlios.de/">C++ wrapper
18    based on the gdome2 bindings</a> maintained by Tobias Peters.</li>
19  <li>and a third C++ wrapper by Peter Jones &lt;pjones@pmade.org&gt;
20    <p>Website: <a href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p>
21  </li>
22  <li><a href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt
23    Sergeant</a> developed <a href="http://axkit.org/download/">XML::LibXSLT</a>, a Perl wrapper for
24    libxml2/libxslt as part of the <a href="http://axkit.com/">AxKit XML
25    application server</a>.</li>
26  <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
27    Libxml2 Perl bindings.</li>
28  <li><a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a> provides an
29    earlier version of the libxml/libxslt <a href="http://www.rexx.com/~dkuhlman">wrappers for Python</a>.</li>
30  <li>Gopal.V and Peter Minten develop <a href="http://savannah.gnu.org/projects/libxmlsharp">libxml#</a>, a set of
31    C# libxml2 bindings.</li>
32  <li>Petr Kozelka provides <a href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue
33    libxml2</a> with Kylix, Delphi and other Pascal compilers.</li>
34  <li>Uwe Fechner also provides <a href="http://sourceforge.net/projects/idom2-pas/">idom2</a>, a DOM2
35    implementation for Kylix2/D5/D6 from Borland.</li>
36  <li>There is <a href="http://rubyforge.org/projects/xml-tools/">bindings for Ruby</a>  and
37    libxml2 bindings are also available in Ruby through the <a href="http://libgdome-ruby.berlios.de/">libgdome-ruby</a> module
38    maintained by Tobias Peters.</li>
39  <li>Steve Ball and contributors maintains <a href="http://tclxml.sourceforge.net/">libxml2 and libxslt bindings for
40    Tcl</a>.</li>
41  <li>libxml2 and libxslt is the default XML library for PHP5.</li>
42  <li><a href="http://savannah.gnu.org/projects/classpathx/">LibxmlJ</a> is
43    an effort to create a 100% JAXP-compatible Java wrapper for libxml2 and
44    libxslt as part of GNU ClasspathX project.</li>
45  <li>Patrick McPhee provides Rexx bindings fof libxml2 and libxslt, look for
46    <a href="http://www.interlog.com/~ptjm/software.html">RexxXML</a>.</li>
47  <li><a href="http://www.satimage.fr/software/en/xml_suite.html">Satimage</a>
48    provides <a href="http://www.satimage.fr/software/en/downloads_osaxen.html">XMLLib
49    osax</a>. This is an osax for Mac OS X with a set of commands to
50    implement in AppleScript the XML DOM, XPATH and XSLT. Also includes
51    commands for Property-lists (Apple's fast lookup table XML format.)</li>
52  <li>Francesco Montorsi developped
53<a href="https://sourceforge.net/project/showfiles.php?group_id=51305&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
57to be maintained as part of the library in the future, though the Python
58interface 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
59bindings, rather than complaining I suggest they have a look at 
60<a href="http://codespeak.net/lxml/">lxml</a> and help Martijn Faassen
61complete those more pythonic bindings for libxml2 and libxslt.</p><p><a href="mailto:stephane.bidoul@softwareag.com">St�phane Bidoul</a>
62maintains <a href="http://users.skynet.be/sbi/libxml-python/">a Windows port
63of the Python bindings</a>.</p><p>Note to people interested in building bindings, the API is formalized as
64<a href="libxml2-api.xml">an XML API description file</a> which allows to
65automate a large part of the Python bindings, this includes function
66descriptions, enums, structures, typedefs, etc... The Python script used to
67build 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
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/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
76python bindings in the <code>python/tests</code> directory. Here are some
77excerpts 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
79doc = libxml2.parseFile("tst.xml")
80if doc.name != "tst.xml":
81    print "doc.name failed"
82    sys.exit(1)
83root = doc.children
84if root.name != "doc":
85    print "root.name failed"
86    sys.exit(1)
87child = root.children
88if child.name != "foo":
89    print "child.name failed"
90    sys.exit(1)
91doc.freeDoc()</pre><p>The Python module is called libxml2; parseFile is the equivalent of
92xmlParseFile (most of the bindings are automatically generated, and the xml
93prefix is removed and the casing convention are kept). All node seen at the
94binding level share the same subset of accessors:</p><ul><li><code>name</code> : returns the node name</li>
95  <li><code>type</code> : returns a string indicating the node type</li>
96  <li><code>content</code> : returns the content of the node, it is based on
97    xmlNodeGetContent() and hence is recursive.</li>
98  <li><code>parent</code> , <code>children</code>, <code>last</code>,
99    <code>next</code>, <code>prev</code>, <code>doc</code>,
100    <code>properties</code>: pointing to the associated element in the tree,
101    those may return None in case no such link exists.</li>
102</ul><p>Also note the need to explicitly deallocate documents with freeDoc() .
103Reference counting for libxml2 trees would need quite a lot of work to
104function properly, and rather than risk memory leaks if not implemented
105correctly it sounds safer to have an explicit function to free a tree. The
106wrapper python objects like doc, root or child are them automatically garbage
107collected.</p><h3>validate.py:</h3><p>This test check the validation interfaces and redirection of error
108messages:</p><pre>import libxml2
109
110#deactivate error messages from the validation
111def noerr(ctx, str):
112    pass
113
114libxml2.registerErrorHandler(noerr, None)
115
116ctxt = libxml2.createFileParserCtxt("invalid.xml")
117ctxt.validate(1)
118ctxt.parseDocument()
119doc = ctxt.doc()
120valid = ctxt.isValid()
121doc.freeDoc()
122if valid != 0:
123    print "validity check failed"</pre><p>The first thing to notice is the call to registerErrorHandler(), it
124defines a new error handler global to the library. It is used to avoid seeing
125the 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
126createFileParserCtxt() and how the behaviour can be changed before calling
127parseDocument() . Similarly the informations resulting from the parsing phase
128are also available using context methods.</p><p>Contexts like nodes are defined as class and the libxml2 wrappers maps the
129C function interfaces in terms of objects method as much as possible. The
130best to get a complete view of what methods are supported is to look at the
131libxml2.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
132
133ctxt = libxml2.createPushParser(None, "&lt;foo", 4, "test.xml")
134ctxt.parseChunk("/&gt;", 2, 1)
135doc = ctxt.doc()
136
137doc.freeDoc()</pre><p>The context is created with a special call based on the
138xmlCreatePushParser() from the C library. The first argument is an optional
139SAX callback object, then the initial set of data, the length and the name of
140the 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
141setting 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
142the parser does not build a document, but provides callback information as
143the parser makes progresses analyzing the data being provided:</p><pre>import libxml2
144log = ""
145
146class callback:
147    def startDocument(self):
148        global log
149        log = log + "startDocument:"
150
151    def endDocument(self):
152        global log
153        log = log + "endDocument:"
154
155    def startElement(self, tag, attrs):
156        global log
157        log = log + "startElement %s %s:" % (tag, attrs)
158
159    def endElement(self, tag):
160        global log
161        log = log + "endElement %s:" % (tag)
162
163    def characters(self, data):
164        global log
165        log = log + "characters: %s:" % (data)
166
167    def warning(self, msg):
168        global log
169        log = log + "warning: %s:" % (msg)
170
171    def error(self, msg):
172        global log
173        log = log + "error: %s:" % (msg)
174
175    def fatalError(self, msg):
176        global log
177        log = log + "fatalError: %s:" % (msg)
178
179handler = callback()
180
181ctxt = libxml2.createPushParser(handler, "&lt;foo", 4, "test.xml")
182chunk = " url='tst'&gt;b"
183ctxt.parseChunk(chunk, len(chunk), 0)
184chunk = "ar&lt;/foo&gt;"
185ctxt.parseChunk(chunk, len(chunk), 1)
186
187reference = "startDocument:startElement foo {'url': 'tst'}:" + \ 
188            "characters: bar:endElement foo:endDocument:"
189if log != reference:
190    print "Error got: %s" % log
191    print "Expected: %s" % reference</pre><p>The key object in that test is the handler, it provides a number of entry
192points which can be called by the parser as it makes progresses to indicate
193the information set obtained. The full set of callback is larger than what
194the callback class in that specific example implements (see the SAX
195definition for a complete list). The wrapper will only call those supplied by
196the object when activated. The startElement receives the names of the element
197and a dictionary containing the attributes carried by this element.</p><p>Also note that the reference string generated from the callback shows a
198single character call even though the string "bar" is passed to the parser
199from 2 different call to parseChunk()</p><h3>xpath.py:</h3><p>This is a basic test of XPath wrappers support</p><pre>import libxml2
200
201doc = libxml2.parseFile("tst.xml")
202ctxt = doc.xpathNewContext()
203res = ctxt.xpathEval("//*")
204if len(res) != 2:
205    print "xpath query: wrong node set size"
206    sys.exit(1)
207if res[0].name != "doc" or res[1].name != "foo":
208    print "xpath query: wrong node set value"
209    sys.exit(1)
210doc.freeDoc()
211ctxt.xpathFreeContext()</pre><p>This test parses a file, then create an XPath context to evaluate XPath
212expression on it. The xpathEval() method execute an XPath query and returns
213the result mapped in a Python way. String and numbers are natively converted,
214and node sets are returned as a tuple of libxml2 Python nodes wrappers. Like
215the document, the XPath context need to be freed explicitly, also not that
216the result of the XPath query may point back to the document tree and hence
217the 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
218python:</p><pre>import libxml2
219
220def foo(ctx, x):
221    return x + 1
222
223doc = libxml2.parseFile("tst.xml")
224ctxt = doc.xpathNewContext()
225libxml2.registerXPathFunction(ctxt._o, "foo", None, foo)
226res = ctxt.xpathEval("foo(1)")
227if res != 2:
228    print "xpath extension failure"
229doc.freeDoc()
230ctxt.xpathFreeContext()</pre><p>Note how the extension function is registered with the context (but that
231part 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
232function can access the XPath evaluation context:</p><pre>def foo(ctx, x):
233    global called
234
235    #
236    # test that access to the XPath evaluation contexts
237    #
238    pctxt = libxml2.xpathParserContext(_obj=ctx)
239    ctxt = pctxt.context()
240    called = ctxt.function()
241    return x + 1</pre><p>All the interfaces around the XPath parser(or rather evaluation) context
242are not finalized, but it should be sufficient to do contextual work at the
243evaluation point.</p><h3>Memory debugging:</h3><p>last but not least, all tests starts with the following prologue:</p><pre>#memory debug specific
244libxml2.debugMemory(1)</pre><p>and ends with the following epilogue:</p><pre>#memory debug specific
245libxml2.cleanupParser()
246if libxml2.debugMemory(1) == 0:
247    print "OK"
248else:
249    print "Memory leak %d bytes" % (libxml2.debugMemory(1))
250    libxml2.dumpMemory()</pre><p>Those activate the memory debugging interface of libxml2 where all
251allocated block in the library are tracked. The prologue then cleans up the
252library state and checks that all allocated memory has been freed. If not it
253calls 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>
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