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</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://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
forlibxml2,the list below is not exhaustive. Please contact the <a href="http://mail.gnome.org/mailman/listinfo/xml-bindings">xml-bindings@gnome.org</a>(<a href="http://mail.gnome.org/archives/xml-bindings/">archives</a>) inorder
toget updates to this list or to discuss the specific topic of
libxml2orlibxslt wrappers or bindings:</p><ul><li><a href="http://libxmlplusplus.sourceforge.net/">Libxml++</a>seemsthemost
up-to-date C++ bindings for libxml2, check the <a href="http://libxmlplusplus.sourceforge.net/reference/html/hierarchy.html">documentation</a>andthe
<a href="http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/libxmlplusplus/libxml%2b%2b/examples/">examples</a>.</li>
<li>There is another <a href="http://libgdome-cpp.berlios.de/">C++wrapperbased on the gdome2
bindings</a>maintained by Tobias Peters.</li>
<li>and a third C++ wrapper by Peter Jones <pjones@pmade.org>
<p>Website: <a href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p>
</li>
<li><a href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">MattSergeant</a>developed<a href="http://axkit.org/download/">XML::LibXSLT</a>, a Perl
wrapperforlibxml2/libxslt as part of the <a href="http://axkit.com/">AxKitXMLapplication server</a>.</li>
<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
basedonLibxml2 Perl bindings.</li>
<li><a href="mailto:dkuhlman@cutter.rexx.com">Dave
Kuhlman</a>providesanearlier version of the libxml/libxslt <a href="http://www.rexx.com/~dkuhlman">wrappers for Python</a>.</li>
<li>Gopal.V and Peter Minten develop <a href="http://savannah.gnu.org/projects/libxmlsharp">libxml#</a>, a
setofC# libxml2 bindings.</li>
<li>Petr Kozelka provides <a href="http://sourceforge.net/projects/libxml2-pas">Pascal units
togluelibxml2</a>with Kylix, Delphi and other Pascal compilers.</li>
<li>Uwe Fechner also provides <a href="http://sourceforge.net/projects/idom2-pas/">idom2</a>,
aDOM2implementation for Kylix2/D5/D6 from Borland.</li>
<li>There is <a href="http://libxml.rubyforge.org/">bindings forRuby</a>and
libxml2 bindings are also available in Ruby through the <a href="http://libgdome-ruby.berlios.de/">libgdome-ruby</a>modulemaintainedby
Tobias Peters.</li>
<li>Steve Ball and contributors maintains <a href="http://tclxml.sourceforge.net/">libxml2 and libxslt
bindingsforTcl</a>.</li>
<li>libxml2 and libxslt is the default XML library for PHP5.</li>
<li><a href="http://savannah.gnu.org/projects/classpathx/">LibxmlJ</a>isaneffort
to create a 100% JAXP-compatible Java wrapper for libxml2andlibxslt as
part of GNU ClasspathX project.</li>
<li>Patrick McPhee provides Rexx bindings fof libxml2 and libxslt,
lookfor<a href="http://www.interlog.com/~ptjm/software.html">RexxXML</a>.</li>
<li><a href="http://www.satimage.fr/software/en/xml_suite.html">Satimage</a>provides<a href="http://www.satimage.fr/software/en/downloads_osaxen.html">XMLLibosax</a>.This
is an osax for Mac OS X with a set of commands toimplement inAppleScript
the XML DOM, XPATH and XSLT. Also includescommands forProperty-lists
(Apple's fast lookup table XML format.)</li>
<li>Francesco Montorsi developped <a href="https://sourceforge.net/project/showfiles.php?group_id=51305&package_id=45182">wxXml2</a>wrappersthat
interface libxml2, allowing wxWidgets applications toload/save/editXML
instances.</li>
</ul><p>The distribution includes a set of Python bindings, which are
guaranteedtobe maintained as part of the library in the future, though
thePythoninterface have not yet reached the completeness of the C API.</p><p>Note that some of the Python purist dislike the default set
ofPythonbindings, rather than complaining I suggest they have a look at <a href="http://codespeak.net/lxml/">lxml the more pythonic bindings
forlibxml2and libxslt</a>and <a href="http://codespeak.net/mailman/listinfo/lxml-dev">helpMartijnFaassen</a>complete
those.</p><p><a href="mailto:stephane.bidoul@softwareag.com">StéphaneBidoul</a>maintains <a href="http://users.skynet.be/sbi/libxml-python/">aWindows portof the Python
bindings</a>.</p><p>Note to people interested in building bindings, the API is formalized as<a href="libxml2-api.xml">an XML API description file</a>which allows
toautomatea large part of the Python bindings, this includes
functiondescriptions,enums, structures, typedefs, etc... The Python script
used tobuild thebindings 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-pythonRPM</a>(andif
needed the <a href="http://rpmfind.net/linux/rpm2html/search.php?query=libxslt-python">libxslt-pythonRPM</a>).</li>
<li>Otherwise use the <a href="ftp://xmlsoft.org/libxml2/python/">libxml2-pythonmoduledistribution</a>corresponding
to your installed version oflibxml2 andlibxslt. Note that to install it
you will need both libxml2and libxsltinstalled and run "python setup.py
build install" in themodule tree.</li>
</ul><p>The distribution includes a set of examples and regression tests
forthepython bindings in the <code>python/tests</code>directory. Here
aresomeexcerpts 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
doc = libxml2.parseFile("tst.xml")
if doc.name != "tst.xml":
print "doc.name failed"
sys.exit(1)
root = doc.children
if root.name != "doc":
print "root.name failed"
sys.exit(1)
child = root.children
if child.name != "foo":
print "child.name failed"
sys.exit(1)
doc.freeDoc()</pre><p>The Python module is called libxml2; parseFile is the
equivalentofxmlParseFile (most of the bindings are automatically generated,
and thexmlprefix is removed and the casing convention are kept). All node
seen atthebinding level share the same subset of accessors:</p><ul><li><code>name</code>: returns the node name</li>
<li><code>type</code>: returns a string indicating the node type</li>
<li><code>content</code>: returns the content of the node, it is
basedonxmlNodeGetContent() and hence is recursive.</li>
<li><code>parent</code>,
<code>children</code>,<code>last</code>,<code>next</code>,
<code>prev</code>,<code>doc</code>,<code>properties</code>: pointing to
the associatedelement in the tree,those may return None in case no such
linkexists.</li>
</ul><p>Also note the need to explicitly deallocate documents with
freeDoc().Reference counting for libxml2 trees would need quite a lot of
worktofunction properly, and rather than risk memory leaks if
notimplementedcorrectly it sounds safer to have an explicit function to free
atree. Thewrapper python objects like doc, root or child are
themautomatically garbagecollected.</p><h3>validate.py:</h3><p>This test check the validation interfaces and redirection
oferrormessages:</p><pre>import libxml2
#deactivate error messages from the validation
def noerr(ctx, str):
pass
libxml2.registerErrorHandler(noerr, None)
ctxt = libxml2.createFileParserCtxt("invalid.xml")
ctxt.validate(1)
ctxt.parseDocument()
doc = ctxt.doc()
valid = ctxt.isValid()
doc.freeDoc()
if valid != 0:
print "validity check failed"</pre><p>The first thing to notice is the call to registerErrorHandler(),
itdefinesa new error handler global to the library. It is used to avoid
seeingtheerror messages when trying to validate the invalid document.</p><p>The main interest of that test is the creation of a parser
contextwithcreateFileParserCtxt() and how the behaviour can be changed
beforecallingparseDocument() . Similarly the informations resulting from
theparsing phaseare also available using context methods.</p><p>Contexts like nodes are defined as class and the libxml2 wrappers mapstheC
function interfaces in terms of objects method as much as possible.Thebest to
get a complete view of what methods are supported is to look atthelibxml2.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
ctxt = libxml2.createPushParser(None, "<foo", 4, "test.xml")
ctxt.parseChunk("/>", 2, 1)
doc = ctxt.doc()
doc.freeDoc()</pre><p>The context is created with a special call based
onthexmlCreatePushParser() from the C library. The first argument is
anoptionalSAX callback object, then the initial set of data, the length and
thename ofthe resource in case URI-References need to be computed by
theparser.</p><p>Then the data are pushed using the parseChunk() method, the
lastcallsetting the third argument terminate to 1.</p><h3>pushSAX.py:</h3><p>this test show the use of the event based parsing interfaces. In
thiscasethe parser does not build a document, but provides callback
informationasthe parser makes progresses analyzing the data being
provided:</p><pre>import libxml2
log = ""
class callback:
def startDocument(self):
global log
log = log + "startDocument:"
def endDocument(self):
global log
log = log + "endDocument:"
def startElement(self, tag, attrs):
global log
log = log + "startElement %s %s:" % (tag, attrs)
def endElement(self, tag):
global log
log = log + "endElement %s:" % (tag)
def characters(self, data):
global log
log = log + "characters: %s:" % (data)
def warning(self, msg):
global log
log = log + "warning: %s:" % (msg)
def error(self, msg):
global log
log = log + "error: %s:" % (msg)
def fatalError(self, msg):
global log
log = log + "fatalError: %s:" % (msg)
handler = callback()
ctxt = libxml2.createPushParser(handler, "<foo", 4, "test.xml")
chunk = " url='tst'>b"
ctxt.parseChunk(chunk, len(chunk), 0)
chunk = "ar</foo>"
ctxt.parseChunk(chunk, len(chunk), 1)
reference = "startDocument:startElement foo {'url': 'tst'}:" + \
"characters: bar:endElement foo:endDocument:"
if log != reference:
print "Error got: %s" % log
print "Expected: %s" % reference</pre><p>The key object in that test is the handler, it provides a number
ofentrypoints which can be called by the parser as it makes progresses
toindicatethe information set obtained. The full set of callback is larger
thanwhatthe callback class in that specific example implements (see
theSAXdefinition for a complete list). The wrapper will only call those
suppliedbythe object when activated. The startElement receives the names of
theelementand a dictionary containing the attributes carried by this
element.</p><p>Also note that the reference string generated from the callback
showsasingle character call even though the string "bar" is passed to
theparserfrom 2 different call to parseChunk()</p><h3>xpath.py:</h3><p>This is a basic test of XPath wrappers support</p><pre>import libxml2
doc = libxml2.parseFile("tst.xml")
ctxt = doc.xpathNewContext()
res = ctxt.xpathEval("//*")
if len(res) != 2:
print "xpath query: wrong node set size"
sys.exit(1)
if res[0].name != "doc" or res[1].name != "foo":
print "xpath query: wrong node set value"
sys.exit(1)
doc.freeDoc()
ctxt.xpathFreeContext()</pre><p>This test parses a file, then create an XPath context to
evaluateXPathexpression on it. The xpathEval() method execute an XPath query
andreturnsthe result mapped in a Python way. String and numbers are
nativelyconverted,and node sets are returned as a tuple of libxml2 Python
nodeswrappers. Likethe document, the XPath context need to be freed
explicitly,also not thatthe result of the XPath query may point back to the
documenttree and hencethe document must be freed after the result of the
query isused.</p><h3>xpathext.py:</h3><p>This test shows how to extend the XPath engine with functions
writteninpython:</p><pre>import libxml2
def foo(ctx, x):
return x + 1
doc = libxml2.parseFile("tst.xml")
ctxt = doc.xpathNewContext()
libxml2.registerXPathFunction(ctxt._o, "foo", None, foo)
res = ctxt.xpathEval("foo(1)")
if res != 2:
print "xpath extension failure"
doc.freeDoc()
ctxt.xpathFreeContext()</pre><p>Note how the extension function is registered with the context
(butthatpart 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
theextensionfunction can access the XPath evaluation context:</p><pre>def foo(ctx, x):
global called
#
# test that access to the XPath evaluation contexts
#
pctxt = libxml2.xpathParserContext(_obj=ctx)
ctxt = pctxt.context()
called = ctxt.function()
return x + 1</pre><p>All the interfaces around the XPath parser(or rather evaluation)contextare
not finalized, but it should be sufficient to do contextual workat
theevaluation point.</p><h3>Memory debugging:</h3><p>last but not least, all tests starts with the following prologue:</p><pre>#memory debug specific
libxml2.debugMemory(1)</pre><p>and ends with the following epilogue:</p><pre>#memory debug specific
libxml2.cleanupParser()
if libxml2.debugMemory(1) == 0:
print "OK"
else:
print "Memory leak %d bytes" % (libxml2.debugMemory(1))
libxml2.dumpMemory()</pre><p>Those activate the memory debugging interface of libxml2 whereallallocated
block in the library are tracked. The prologue then cleans upthelibrary state
and checks that all allocated memory has been freed. If notitcalls
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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