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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://opencsw.org/packages/libxml2">Solaris binaries</a></li><li><a href="http://www.explain.com.au/oss/libxml2xslt.html">MacOsX binaries</a></li><li><a href="http://codespeak.net/lxml/">lxml Python bindings</a></li><li><a href="http://cpan.uwinnipeg.ca/dist/XML-LibXML">Perl bindings</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://libxml.rubyforge.org/">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
11 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>
12 (<a href="http://mail.gnome.org/archives/xml-bindings/">archives</a>) in
13 order to get updates to this list or to discuss the specific topic of libxml2
14 or 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 <pjones@pmade.org>
20 <p>Website: <a href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p>
22 <li>XML::LibXML <a href="http://cpan.uwinnipeg.ca/dist/XML-LibXML">Perl
23 bindings</a> are available on CPAN, as well as XML::LibXSLT
24 <a href="http://cpan.uwinnipeg.ca/dist/XML-LibXSLT">Perl libxslt
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://libxml.rubyforge.org/">bindings for Ruby</a>
37 and 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
41 <li>libxml2 and libxslt are the default XML libraries 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 <a href="https://sourceforge.net/project/showfiles.php?group_id=51305&package_id=45182">wxXml2</a>
53 wrappers that interface libxml2, allowing wxWidgets applications to
54 load/save/edit XML instances.</li>
55 </ul><p>The distribution includes a set of Python bindings, which are guaranteed
56 to be maintained as part of the library in the future, though the Python
57 interface 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
58 bindings, rather than complaining I suggest they have a look at <a href="http://codespeak.net/lxml/">lxml the more pythonic bindings for libxml2
59 and libxslt</a> and <a href="http://codespeak.net/mailman/listinfo/lxml-dev">help Martijn
60 Faassen</a> complete those.</p><p><a href="mailto:stephane.bidoul@softwareag.com">Stéphane Bidoul</a>
61 maintains <a href="http://users.skynet.be/sbi/libxml-python/">a Windows port
62 of the Python bindings</a>.</p><p>Note to people interested in building bindings, the API is formalized as
63 <a href="libxml2-api.xml">an XML API description file</a> which allows to
64 automate a large part of the Python bindings, this includes function
65 descriptions, enums, structures, typedefs, etc... The Python script used to
66 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
67 RPM</a> (and if needed the <a href="http://rpmfind.net/linux/rpm2html/search.php?query=libxslt-python">libxslt-python
69 <li>Otherwise use the <a href="ftp://xmlsoft.org/libxml2/python/">libxml2-python
70 module distribution</a> corresponding to your installed version of
71 libxml2 and libxslt. Note that to install it you will need both libxml2
72 and libxslt installed and run "python setup.py build install" in the
74 </ul><p>The distribution includes a set of examples and regression tests for the
75 python bindings in the <code>python/tests</code> directory. Here are some
76 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, sys
78 doc = libxml2.parseFile("tst.xml")
79 if doc.name != "tst.xml":
80 print "doc.name failed"
83 if root.name != "doc":
84 print "root.name failed"
87 if child.name != "foo":
88 print "child.name failed"
90 doc.freeDoc()</pre><p>The Python module is called libxml2; parseFile is the equivalent of
91 xmlParseFile (most of the bindings are automatically generated, and the xml
92 prefix is removed and the casing convention are kept). All node seen at the
93 binding level share the same subset of accessors:</p><ul><li><code>name</code> : returns the node name</li>
94 <li><code>type</code> : returns a string indicating the node type</li>
95 <li><code>content</code> : returns the content of the node, it is based on
96 xmlNodeGetContent() and hence is recursive.</li>
97 <li><code>parent</code> , <code>children</code>, <code>last</code>,
98 <code>next</code>, <code>prev</code>, <code>doc</code>,
99 <code>properties</code>: pointing to the associated element in the tree,
100 those may return None in case no such link exists.</li>
101 </ul><p>Also note the need to explicitly deallocate documents with freeDoc() .
102 Reference counting for libxml2 trees would need quite a lot of work to
103 function properly, and rather than risk memory leaks if not implemented
104 correctly it sounds safer to have an explicit function to free a tree. The
105 wrapper python objects like doc, root or child are them automatically garbage
106 collected.</p><h3>validate.py:</h3><p>This test check the validation interfaces and redirection of error
107 messages:</p><pre>import libxml2
109 #deactivate error messages from the validation
113 libxml2.registerErrorHandler(noerr, None)
115 ctxt = libxml2.createFileParserCtxt("invalid.xml")
119 valid = ctxt.isValid()
122 print "validity check failed"</pre><p>The first thing to notice is the call to registerErrorHandler(), it
123 defines a new error handler global to the library. It is used to avoid seeing
124 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
125 createFileParserCtxt() and how the behaviour can be changed before calling
126 parseDocument() . Similarly the information resulting from the parsing phase
127 is also available using context methods.</p><p>Contexts like nodes are defined as class and the libxml2 wrappers maps the
128 C function interfaces in terms of objects method as much as possible. The
129 best to get a complete view of what methods are supported is to look at the
130 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
132 ctxt = libxml2.createPushParser(None, "<foo", 4, "test.xml")
133 ctxt.parseChunk("/>", 2, 1)
136 doc.freeDoc()</pre><p>The context is created with a special call based on the
137 xmlCreatePushParser() from the C library. The first argument is an optional
138 SAX callback object, then the initial set of data, the length and the name of
139 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
140 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
141 the parser does not build a document, but provides callback information as
142 the parser makes progresses analyzing the data being provided:</p><pre>import libxml2
146 def startDocument(self):
148 log = log + "startDocument:"
150 def endDocument(self):
152 log = log + "endDocument:"
154 def startElement(self, tag, attrs):
156 log = log + "startElement %s %s:" % (tag, attrs)
158 def endElement(self, tag):
160 log = log + "endElement %s:" % (tag)
162 def characters(self, data):
164 log = log + "characters: %s:" % (data)
166 def warning(self, msg):
168 log = log + "warning: %s:" % (msg)
170 def error(self, msg):
172 log = log + "error: %s:" % (msg)
174 def fatalError(self, msg):
176 log = log + "fatalError: %s:" % (msg)
180 ctxt = libxml2.createPushParser(handler, "<foo", 4, "test.xml")
181 chunk = " url='tst'>b"
182 ctxt.parseChunk(chunk, len(chunk), 0)
183 chunk = "ar</foo>"
184 ctxt.parseChunk(chunk, len(chunk), 1)
186 reference = "startDocument:startElement foo {'url': 'tst'}:" + \
187 "characters: bar:endElement foo:endDocument:"
189 print "Error got: %s" % log
190 print "Expected: %s" % reference</pre><p>The key object in that test is the handler, it provides a number of entry
191 points which can be called by the parser as it makes progresses to indicate
192 the information set obtained. The full set of callback is larger than what
193 the callback class in that specific example implements (see the SAX
194 definition for a complete list). The wrapper will only call those supplied by
195 the object when activated. The startElement receives the names of the element
196 and a dictionary containing the attributes carried by this element.</p><p>Also note that the reference string generated from the callback shows a
197 single character call even though the string "bar" is passed to the parser
198 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
200 doc = libxml2.parseFile("tst.xml")
201 ctxt = doc.xpathNewContext()
202 res = ctxt.xpathEval("//*")
204 print "xpath query: wrong node set size"
206 if res[0].name != "doc" or res[1].name != "foo":
207 print "xpath query: wrong node set value"
210 ctxt.xpathFreeContext()</pre><p>This test parses a file, then create an XPath context to evaluate XPath
211 expression on it. The xpathEval() method execute an XPath query and returns
212 the result mapped in a Python way. String and numbers are natively converted,
213 and node sets are returned as a tuple of libxml2 Python nodes wrappers. Like
214 the document, the XPath context need to be freed explicitly, also not that
215 the result of the XPath query may point back to the document tree and hence
216 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
217 python:</p><pre>import libxml2
222 doc = libxml2.parseFile("tst.xml")
223 ctxt = doc.xpathNewContext()
224 libxml2.registerXPathFunction(ctxt._o, "foo", None, foo)
225 res = ctxt.xpathEval("foo(1)")
227 print "xpath extension failure"
229 ctxt.xpathFreeContext()</pre><p>Note how the extension function is registered with the context (but that
230 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
231 function can access the XPath evaluation context:</p><pre>def foo(ctx, x):
235 # test that access to the XPath evaluation contexts
237 pctxt = libxml2.xpathParserContext(_obj=ctx)
238 ctxt = pctxt.context()
239 called = ctxt.function()
240 return x + 1</pre><p>All the interfaces around the XPath parser(or rather evaluation) context
241 are not finalized, but it should be sufficient to do contextual work at the
242 evaluation point.</p><h3>Memory debugging:</h3><p>last but not least, all tests starts with the following prologue:</p><pre>#memory debug specific
243 libxml2.debugMemory(1)</pre><p>and ends with the following epilogue:</p><pre>#memory debug specific
244 libxml2.cleanupParser()
245 if libxml2.debugMemory(1) == 0:
248 print "Memory leak %d bytes" % (libxml2.debugMemory(1))
249 libxml2.dumpMemory()</pre><p>Those activate the memory debugging interface of libxml2 where all
250 allocated block in the library are tracked. The prologue then cleans up the
251 library state and checks that all allocated memory has been freed. If not it
252 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>
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