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><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>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, "<foo", 4, "test.xml") 132ctxt.parseChunk("/>", 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, "<foo", 4, "test.xml") 180chunk = " url='tst'>b" 181ctxt.parseChunk(chunk, len(chunk), 0) 182chunk = "ar</foo>" 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
