1<?xml version="1.0" encoding="UTF-8"?>
2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
3<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><link rel="SHORTCUT ICON" href="/favicon.ico" /><style type="text/css">
4TD {font-family: Verdana,Arial,Helvetica}
5BODY {font-family: Verdana,Arial,Helvetica; margin-top: 2em; margin-left: 0em; margin-right: 0em}
6H1 {font-family: Verdana,Arial,Helvetica}
7H2 {font-family: Verdana,Arial,Helvetica}
8H3 {font-family: Verdana,Arial,Helvetica}
9A:link, A:visited, A:active { text-decoration: underline }
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 Examples</a></li><li><a href="guidelines.html">XML Guidelines</a></li><li><a href="tutorial/index.html">Tutorial</a></li><li><a href="xmlreader.html">The Reader Interface</a></li><li><a href="ChangeLog.html">ChangeLog</a></li><li><a href="XSLT.html">XSLT</a></li><li><a href="python.html">Python and bindings</a></li><li><a href="architecture.html">libxml2 architecture</a></li><li><a href="tree.html">The tree output</a></li><li><a href="interface.html">The SAX interface</a></li><li><a href="xmlmem.html">Memory Management</a></li><li><a href="xmlio.html">I/O Interfaces</a></li><li><a href="library.html">The parser interfaces</a></li><li><a href="entities.html">Entities or no entities</a></li><li><a href="namespaces.html">Namespaces</a></li><li><a href="upgrade.html">Upgrading 1.x code</a></li><li><a href="threads.html">Thread safety</a></li><li><a href="DOM.html">DOM Principles</a></li><li><a href="example.html">A real example</a></li><li><a href="xml.html">flat page</a>, <a 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://lxml.de/">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
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>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
25      bindings</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://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
40    Tcl</a>.</li>
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
56to be maintained as part of the library in the future, though the Python
57interface 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
58bindings, rather than complaining I suggest they have a look at <a href="http://lxml.de/">lxml the more pythonic bindings for libxml2
59and libxslt</a> and <a href="http://lxml.de/mailinglist/">check the mailing-list</a>.</p><p><a href="mailto:stephane.bidoul@softwareag.com">Stéphane Bidoul</a>
60maintains <a href="http://users.skynet.be/sbi/libxml-python/">a Windows port
61of the Python bindings</a>.</p><p>Note to people interested in building bindings, the API is formalized as
62<a href="libxml2-api.xml">an XML API description file</a> which allows to
63automate a large part of the Python bindings, this includes function
64descriptions, enums, structures, typedefs, etc... The Python script used to
65build 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
66    RPM</a> (and if needed the <a href="http://rpmfind.net/linux/rpm2html/search.php?query=libxslt-python">libxslt-python
67    RPM</a>).</li>
68  <li>Otherwise use the <a href="ftp://xmlsoft.org/libxml2/python/">libxml2-python
69    module distribution</a> corresponding to your installed version of
70    libxml2 and libxslt. Note that to install it you will need both libxml2
71    and libxslt installed and run "python setup.py build install" in the
72    module tree.</li>
73</ul><p>The distribution includes a set of examples and regression tests for the
74python bindings in the <code>python/tests</code> directory. Here are some
75excerpts 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
76
77doc = libxml2.parseFile("tst.xml")
78if doc.name != "tst.xml":
79    print "doc.name failed"
80    sys.exit(1)
81root = doc.children
82if root.name != "doc":
83    print "root.name failed"
84    sys.exit(1)
85child = root.children
86if child.name != "foo":
87    print "child.name failed"
88    sys.exit(1)
89doc.freeDoc()</pre><p>The Python module is called libxml2; parseFile is the equivalent of
90xmlParseFile (most of the bindings are automatically generated, and the xml
91prefix is removed and the casing convention are kept). All node seen at the
92binding level share the same subset of accessors:</p><ul><li><code>name</code> : returns the node name</li>
93  <li><code>type</code> : returns a string indicating the node type</li>
94  <li><code>content</code> : returns the content of the node, it is based on
95    xmlNodeGetContent() and hence is recursive.</li>
96  <li><code>parent</code> , <code>children</code>, <code>last</code>,
97    <code>next</code>, <code>prev</code>, <code>doc</code>,
98    <code>properties</code>: pointing to the associated element in the tree,
99    those may return None in case no such link exists.</li>
100</ul><p>Also note the need to explicitly deallocate documents with freeDoc() .
101Reference counting for libxml2 trees would need quite a lot of work to
102function properly, and rather than risk memory leaks if not implemented
103correctly it sounds safer to have an explicit function to free a tree. The
104wrapper python objects like doc, root or child are them automatically garbage
105collected.</p><h3>validate.py:</h3><p>This test check the validation interfaces and redirection of error
106messages:</p><pre>import libxml2
107
108#deactivate error messages from the validation
109def noerr(ctx, str):
110    pass
111
112libxml2.registerErrorHandler(noerr, None)
113
114ctxt = libxml2.createFileParserCtxt("invalid.xml")
115ctxt.validate(1)
116ctxt.parseDocument()
117doc = ctxt.doc()
118valid = ctxt.isValid()
119doc.freeDoc()
120if valid != 0:
121    print "validity check failed"</pre><p>The first thing to notice is the call to registerErrorHandler(), it
122defines a new error handler global to the library. It is used to avoid seeing
123the 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
124createFileParserCtxt() and how the behaviour can be changed before calling
125parseDocument() . Similarly the information resulting from the parsing phase
126is also available using context methods.</p><p>Contexts like nodes are defined as class and the libxml2 wrappers maps the
127C function interfaces in terms of objects method as much as possible. The
128best to get a complete view of what methods are supported is to look at the
129libxml2.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
130
131ctxt = libxml2.createPushParser(None, "&lt;foo", 4, "test.xml")
132ctxt.parseChunk("/&gt;", 2, 1)
133doc = ctxt.doc()
134
135doc.freeDoc()</pre><p>The context is created with a special call based on the
136xmlCreatePushParser() from the C library. The first argument is an optional
137SAX callback object, then the initial set of data, the length and the name of
138the 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
139setting 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
140the parser does not build a document, but provides callback information as
141the parser makes progresses analyzing the data being provided:</p><pre>import libxml2
142log = ""
143
144class callback:
145    def startDocument(self):
146        global log
147        log = log + "startDocument:"
148
149    def endDocument(self):
150        global log
151        log = log + "endDocument:"
152
153    def startElement(self, tag, attrs):
154        global log
155        log = log + "startElement %s %s:" % (tag, attrs)
156
157    def endElement(self, tag):
158        global log
159        log = log + "endElement %s:" % (tag)
160
161    def characters(self, data):
162        global log
163        log = log + "characters: %s:" % (data)
164
165    def warning(self, msg):
166        global log
167        log = log + "warning: %s:" % (msg)
168
169    def error(self, msg):
170        global log
171        log = log + "error: %s:" % (msg)
172
173    def fatalError(self, msg):
174        global log
175        log = log + "fatalError: %s:" % (msg)
176
177handler = callback()
178
179ctxt = libxml2.createPushParser(handler, "&lt;foo", 4, "test.xml")
180chunk = " url='tst'&gt;b"
181ctxt.parseChunk(chunk, len(chunk), 0)
182chunk = "ar&lt;/foo&gt;"
183ctxt.parseChunk(chunk, len(chunk), 1)
184
185reference = "startDocument:startElement foo {'url': 'tst'}:" + \ 
186            "characters: bar:endElement foo:endDocument:"
187if log != reference:
188    print "Error got: %s" % log
189    print "Expected: %s" % reference</pre><p>The key object in that test is the handler, it provides a number of entry
190points which can be called by the parser as it makes progresses to indicate
191the information set obtained. The full set of callback is larger than what
192the callback class in that specific example implements (see the SAX
193definition for a complete list). The wrapper will only call those supplied by
194the object when activated. The startElement receives the names of the element
195and a dictionary containing the attributes carried by this element.</p><p>Also note that the reference string generated from the callback shows a
196single character call even though the string "bar" is passed to the parser
197from 2 different call to parseChunk()</p><h3>xpath.py:</h3><p>This is a basic test of XPath wrappers support</p><pre>import libxml2
198
199doc = libxml2.parseFile("tst.xml")
200ctxt = doc.xpathNewContext()
201res = ctxt.xpathEval("//*")
202if len(res) != 2:
203    print "xpath query: wrong node set size"
204    sys.exit(1)
205if res[0].name != "doc" or res[1].name != "foo":
206    print "xpath query: wrong node set value"
207    sys.exit(1)
208doc.freeDoc()
209ctxt.xpathFreeContext()</pre><p>This test parses a file, then create an XPath context to evaluate XPath
210expression on it. The xpathEval() method execute an XPath query and returns
211the result mapped in a Python way. String and numbers are natively converted,
212and node sets are returned as a tuple of libxml2 Python nodes wrappers. Like
213the document, the XPath context need to be freed explicitly, also not that
214the result of the XPath query may point back to the document tree and hence
215the 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
216python:</p><pre>import libxml2
217
218def foo(ctx, x):
219    return x + 1
220
221doc = libxml2.parseFile("tst.xml")
222ctxt = doc.xpathNewContext()
223libxml2.registerXPathFunction(ctxt._o, "foo", None, foo)
224res = ctxt.xpathEval("foo(1)")
225if res != 2:
226    print "xpath extension failure"
227doc.freeDoc()
228ctxt.xpathFreeContext()</pre><p>Note how the extension function is registered with the context (but that
229part 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
230function can access the XPath evaluation context:</p><pre>def foo(ctx, x):
231    global called
232
233    #
234    # test that access to the XPath evaluation contexts
235    #
236    pctxt = libxml2.xpathParserContext(_obj=ctx)
237    ctxt = pctxt.context()
238    called = ctxt.function()
239    return x + 1</pre><p>All the interfaces around the XPath parser(or rather evaluation) context
240are not finalized, but it should be sufficient to do contextual work at the
241evaluation point.</p><h3>Memory debugging:</h3><p>last but not least, all tests starts with the following prologue:</p><pre>#memory debug specific
242libxml2.debugMemory(1)</pre><p>and ends with the following epilogue:</p><pre>#memory debug specific
243libxml2.cleanupParser()
244if libxml2.debugMemory(1) == 0:
245    print "OK"
246else:
247    print "Memory leak %d bytes" % (libxml2.debugMemory(1))
248    libxml2.dumpMemory()</pre><p>Those activate the memory debugging interface of libxml2 where all
249allocated block in the library are tracked. The prologue then cleans up the
250library state and checks that all allocated memory has been freed. If not it
251calls 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>
252