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1<?xml version="1.0" encoding="ISO-8859-1"?> 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=ISO-8859-1" /><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://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 <pjones@pmade.org> 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, "<foo", 4, "test.xml") 134ctxt.parseChunk("/>", 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, "<foo", 4, "test.xml") 182chunk = " url='tst'>b" 183ctxt.parseChunk(chunk, len(chunk), 0) 184chunk = "ar</foo>" 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> 254