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" 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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> 15 <li><a href="http://libxmlplusplus.sourceforge.net/">Libxml++</a> seems the 16 most up-to-date C++ bindings for libxml2, check the <a href="http://libxmlplusplus.sourceforge.net/reference/html/hierarchy.html">documentation</a> 17 and the <a href="http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/libxmlplusplus/libxml%2b%2b/examples/">examples</a>.</li> 18 <li>There is another <a href="http://libgdome-cpp.berlios.de/">C++ wrapper 19 based on the gdome2 bindings</a> maintained by Tobias Peters.</li> 20 <li>and a third C++ wrapper by Peter Jones <pjones@pmade.org> 21 <p>Website: <a href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p> 22 </li> 23 <li>XML::LibXML <a href="http://cpan.uwinnipeg.ca/dist/XML-LibXML">Perl 24 bindings</a> are available on CPAN, as well as XML::LibXSLT 25 <a href="http://cpan.uwinnipeg.ca/dist/XML-LibXSLT">Perl libxslt 26 bindings</a>.</li> 27 <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 28 Libxml2 Perl bindings.</li> 29 <li><a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a> provides an 30 earlier version of the libxml/libxslt <a href="http://www.rexx.com/~dkuhlman">wrappers for Python</a>.</li> 31 <li>Gopal.V and Peter Minten develop <a href="http://savannah.gnu.org/projects/libxmlsharp">libxml#</a>, a set of 32 C# libxml2 bindings.</li> 33 <li>Petr Kozelka provides <a href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue 34 libxml2</a> with Kylix, Delphi and other Pascal compilers.</li> 35 <li>Uwe Fechner also provides <a href="http://sourceforge.net/projects/idom2-pas/">idom2</a>, a DOM2 36 implementation for Kylix2/D5/D6 from Borland.</li> 37 <li>There is <a href="http://libxml.rubyforge.org/">bindings for Ruby</a> 38 and libxml2 bindings are also available in Ruby through the <a href="http://libgdome-ruby.berlios.de/">libgdome-ruby</a> module 39 maintained by Tobias Peters.</li> 40 <li>Steve Ball and contributors maintains <a href="http://tclxml.sourceforge.net/">libxml2 and libxslt bindings for 41 Tcl</a>.</li> 42 <li>libxml2 and libxslt are the default XML libraries for PHP5.</li> 43 <li><a href="http://savannah.gnu.org/projects/classpathx/">LibxmlJ</a> is 44 an effort to create a 100% JAXP-compatible Java wrapper for libxml2 and 45 libxslt as part of GNU ClasspathX project.</li> 46 <li>Patrick McPhee provides Rexx bindings fof libxml2 and libxslt, look for 47 <a href="http://www.interlog.com/~ptjm/software.html">RexxXML</a>.</li> 48 <li><a href="http://www.satimage.fr/software/en/xml_suite.html">Satimage</a> 49 provides <a href="http://www.satimage.fr/software/en/downloads_osaxen.html">XMLLib 50 osax</a>. This is an osax for Mac OS X with a set of commands to 51 implement in AppleScript the XML DOM, XPATH and XSLT. Also includes 52 commands for Property-lists (Apple's fast lookup table XML format.)</li> 53 <li>Francesco Montorsi developped <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 <a href="http://lxml.de/">lxml the more pythonic bindings for libxml2 60and 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> 61maintains <a href="http://users.skynet.be/sbi/libxml-python/">a Windows port 62of 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 64automate a large part of the Python bindings, this includes function 65descriptions, enums, structures, typedefs, etc... The Python script used to 66build the bindings is python/generator.py in the source distribution.</p><p>To install the Python bindings there are 2 options:</p><ul> 67 <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/libxml2/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> 95 <li><code>name</code> : returns the node name</li> 96 <li><code>type</code> : returns a string indicating the node type</li> 97 <li><code>content</code> : returns the content of the node, it is based on 98 xmlNodeGetContent() and hence is recursive.</li> 99 <li><code>parent</code> , <code>children</code>, <code>last</code>, 100 <code>next</code>, <code>prev</code>, <code>doc</code>, 101 <code>properties</code>: pointing to the associated element in the tree, 102 those may return None in case no such link exists.</li> 103</ul><p>Also note the need to explicitly deallocate documents with freeDoc() . 104Reference counting for libxml2 trees would need quite a lot of work to 105function properly, and rather than risk memory leaks if not implemented 106correctly it sounds safer to have an explicit function to free a tree. The 107wrapper python objects like doc, root or child are them automatically garbage 108collected.</p><h3>validate.py:</h3><p>This test check the validation interfaces and redirection of error 109messages:</p><pre>import libxml2 110 111#deactivate error messages from the validation 112def noerr(ctx, str): 113 pass 114 115libxml2.registerErrorHandler(noerr, None) 116 117ctxt = libxml2.createFileParserCtxt("invalid.xml") 118ctxt.validate(1) 119ctxt.parseDocument() 120doc = ctxt.doc() 121valid = ctxt.isValid() 122doc.freeDoc() 123if valid != 0: 124 print "validity check failed"</pre><p>The first thing to notice is the call to registerErrorHandler(), it 125defines a new error handler global to the library. It is used to avoid seeing 126the 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 127createFileParserCtxt() and how the behaviour can be changed before calling 128parseDocument() . Similarly the information resulting from the parsing phase 129is also available using context methods.</p><p>Contexts like nodes are defined as class and the libxml2 wrappers maps the 130C function interfaces in terms of objects method as much as possible. The 131best to get a complete view of what methods are supported is to look at the 132libxml2.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 133 134ctxt = libxml2.createPushParser(None, "<foo", 4, "test.xml") 135ctxt.parseChunk("/>", 2, 1) 136doc = ctxt.doc() 137 138doc.freeDoc()</pre><p>The context is created with a special call based on the 139xmlCreatePushParser() from the C library. The first argument is an optional 140SAX callback object, then the initial set of data, the length and the name of 141the 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 142setting 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 143the parser does not build a document, but provides callback information as 144the parser makes progresses analyzing the data being provided:</p><pre>import libxml2 145log = "" 146 147class callback: 148 def startDocument(self): 149 global log 150 log = log + "startDocument:" 151 152 def endDocument(self): 153 global log 154 log = log + "endDocument:" 155 156 def startElement(self, tag, attrs): 157 global log 158 log = log + "startElement %s %s:" % (tag, attrs) 159 160 def endElement(self, tag): 161 global log 162 log = log + "endElement %s:" % (tag) 163 164 def characters(self, data): 165 global log 166 log = log + "characters: %s:" % (data) 167 168 def warning(self, msg): 169 global log 170 log = log + "warning: %s:" % (msg) 171 172 def error(self, msg): 173 global log 174 log = log + "error: %s:" % (msg) 175 176 def fatalError(self, msg): 177 global log 178 log = log + "fatalError: %s:" % (msg) 179 180handler = callback() 181 182ctxt = libxml2.createPushParser(handler, "<foo", 4, "test.xml") 183chunk = " url='tst'>b" 184ctxt.parseChunk(chunk, len(chunk), 0) 185chunk = "ar</foo>" 186ctxt.parseChunk(chunk, len(chunk), 1) 187 188reference = "startDocument:startElement foo {'url': 'tst'}:" + \ 189 "characters: bar:endElement foo:endDocument:" 190if log != reference: 191 print "Error got: %s" % log 192 print "Expected: %s" % reference</pre><p>The key object in that test is the handler, it provides a number of entry 193points which can be called by the parser as it makes progresses to indicate 194the information set obtained. The full set of callback is larger than what 195the callback class in that specific example implements (see the SAX 196definition for a complete list). The wrapper will only call those supplied by 197the object when activated. The startElement receives the names of the element 198and a dictionary containing the attributes carried by this element.</p><p>Also note that the reference string generated from the callback shows a 199single character call even though the string "bar" is passed to the parser 200from 2 different call to parseChunk()</p><h3>xpath.py:</h3><p>This is a basic test of XPath wrappers support</p><pre>import libxml2 201 202doc = libxml2.parseFile("tst.xml") 203ctxt = doc.xpathNewContext() 204res = ctxt.xpathEval("//*") 205if len(res) != 2: 206 print "xpath query: wrong node set size" 207 sys.exit(1) 208if res[0].name != "doc" or res[1].name != "foo": 209 print "xpath query: wrong node set value" 210 sys.exit(1) 211doc.freeDoc() 212ctxt.xpathFreeContext()</pre><p>This test parses a file, then create an XPath context to evaluate XPath 213expression on it. The xpathEval() method execute an XPath query and returns 214the result mapped in a Python way. String and numbers are natively converted, 215and node sets are returned as a tuple of libxml2 Python nodes wrappers. Like 216the document, the XPath context need to be freed explicitly, also not that 217the result of the XPath query may point back to the document tree and hence 218the 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 219python:</p><pre>import libxml2 220 221def foo(ctx, x): 222 return x + 1 223 224doc = libxml2.parseFile("tst.xml") 225ctxt = doc.xpathNewContext() 226libxml2.registerXPathFunction(ctxt._o, "foo", None, foo) 227res = ctxt.xpathEval("foo(1)") 228if res != 2: 229 print "xpath extension failure" 230doc.freeDoc() 231ctxt.xpathFreeContext()</pre><p>Note how the extension function is registered with the context (but that 232part 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 233function can access the XPath evaluation context:</p><pre>def foo(ctx, x): 234 global called 235 236 # 237 # test that access to the XPath evaluation contexts 238 # 239 pctxt = libxml2.xpathParserContext(_obj=ctx) 240 ctxt = pctxt.context() 241 called = ctxt.function() 242 return x + 1</pre><p>All the interfaces around the XPath parser(or rather evaluation) context 243are not finalized, but it should be sufficient to do contextual work at the 244evaluation point.</p><h3>Memory debugging:</h3><p>last but not least, all tests starts with the following prologue:</p><pre>#memory debug specific 245libxml2.debugMemory(1)</pre><p>and ends with the following epilogue:</p><pre>#memory debug specific 246libxml2.cleanupParser() 247if libxml2.debugMemory(1) == 0: 248 print "OK" 249else: 250 print "Memory leak %d bytes" % (libxml2.debugMemory(1)) 251 libxml2.dumpMemory()</pre><p>Those activate the memory debugging interface of libxml2 where all 252allocated block in the library are tracked. The prologue then cleans up the 253library state and checks that all allocated memory has been freed. If not it 254calls 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> 255
