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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 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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://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
11: libxml2, 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
13: order to get updates to this list or to discuss the specific topic of libxml2
14: or 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
56: to be maintained as part of the library in the future, though the Python
57: interface 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
58: bindings, rather than complaining I suggest they have a look at <a href="http://lxml.de/">lxml the more pythonic bindings for libxml2
59: and 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>
60: maintains <a href="http://users.skynet.be/sbi/libxml-python/">a Windows port
61: of 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
63: automate a large part of the Python bindings, this includes function
64: descriptions, enums, structures, typedefs, etc... The Python script used to
65: build 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
74: python bindings in the <code>python/tests</code> directory. Here are some
75: excerpts 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:
77: doc = libxml2.parseFile("tst.xml")
78: if doc.name != "tst.xml":
79: print "doc.name failed"
80: sys.exit(1)
81: root = doc.children
82: if root.name != "doc":
83: print "root.name failed"
84: sys.exit(1)
85: child = root.children
86: if child.name != "foo":
87: print "child.name failed"
88: sys.exit(1)
89: doc.freeDoc()</pre><p>The Python module is called libxml2; parseFile is the equivalent of
90: xmlParseFile (most of the bindings are automatically generated, and the xml
91: prefix is removed and the casing convention are kept). All node seen at the
92: binding 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() .
101: Reference counting for libxml2 trees would need quite a lot of work to
102: function properly, and rather than risk memory leaks if not implemented
103: correctly it sounds safer to have an explicit function to free a tree. The
104: wrapper python objects like doc, root or child are them automatically garbage
105: collected.</p><h3>validate.py:</h3><p>This test check the validation interfaces and redirection of error
106: messages:</p><pre>import libxml2
107:
108: #deactivate error messages from the validation
109: def noerr(ctx, str):
110: pass
111:
112: libxml2.registerErrorHandler(noerr, None)
113:
114: ctxt = libxml2.createFileParserCtxt("invalid.xml")
115: ctxt.validate(1)
116: ctxt.parseDocument()
117: doc = ctxt.doc()
118: valid = ctxt.isValid()
119: doc.freeDoc()
120: if valid != 0:
121: print "validity check failed"</pre><p>The first thing to notice is the call to registerErrorHandler(), it
122: defines a new error handler global to the library. It is used to avoid seeing
123: the 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
124: createFileParserCtxt() and how the behaviour can be changed before calling
125: parseDocument() . Similarly the information resulting from the parsing phase
126: is also available using context methods.</p><p>Contexts like nodes are defined as class and the libxml2 wrappers maps the
127: C function interfaces in terms of objects method as much as possible. The
128: best to get a complete view of what methods are supported is to look at the
129: libxml2.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:
131: ctxt = libxml2.createPushParser(None, "<foo", 4, "test.xml")
132: ctxt.parseChunk("/>", 2, 1)
133: doc = ctxt.doc()
134:
135: doc.freeDoc()</pre><p>The context is created with a special call based on the
136: xmlCreatePushParser() from the C library. The first argument is an optional
137: SAX callback object, then the initial set of data, the length and the name of
138: the 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
139: setting 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
140: the parser does not build a document, but provides callback information as
141: the parser makes progresses analyzing the data being provided:</p><pre>import libxml2
142: log = ""
143:
144: class 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:
177: handler = callback()
178:
179: ctxt = libxml2.createPushParser(handler, "<foo", 4, "test.xml")
180: chunk = " url='tst'>b"
181: ctxt.parseChunk(chunk, len(chunk), 0)
182: chunk = "ar</foo>"
183: ctxt.parseChunk(chunk, len(chunk), 1)
184:
185: reference = "startDocument:startElement foo {'url': 'tst'}:" + \
186: "characters: bar:endElement foo:endDocument:"
187: if 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
190: points which can be called by the parser as it makes progresses to indicate
191: the information set obtained. The full set of callback is larger than what
192: the callback class in that specific example implements (see the SAX
193: definition for a complete list). The wrapper will only call those supplied by
194: the object when activated. The startElement receives the names of the element
195: and a dictionary containing the attributes carried by this element.</p><p>Also note that the reference string generated from the callback shows a
196: single character call even though the string "bar" is passed to the parser
197: from 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:
199: doc = libxml2.parseFile("tst.xml")
200: ctxt = doc.xpathNewContext()
201: res = ctxt.xpathEval("//*")
202: if len(res) != 2:
203: print "xpath query: wrong node set size"
204: sys.exit(1)
205: if res[0].name != "doc" or res[1].name != "foo":
206: print "xpath query: wrong node set value"
207: sys.exit(1)
208: doc.freeDoc()
209: ctxt.xpathFreeContext()</pre><p>This test parses a file, then create an XPath context to evaluate XPath
210: expression on it. The xpathEval() method execute an XPath query and returns
211: the result mapped in a Python way. String and numbers are natively converted,
212: and node sets are returned as a tuple of libxml2 Python nodes wrappers. Like
213: the document, the XPath context need to be freed explicitly, also not that
214: the result of the XPath query may point back to the document tree and hence
215: the 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
216: python:</p><pre>import libxml2
217:
218: def foo(ctx, x):
219: return x + 1
220:
221: doc = libxml2.parseFile("tst.xml")
222: ctxt = doc.xpathNewContext()
223: libxml2.registerXPathFunction(ctxt._o, "foo", None, foo)
224: res = ctxt.xpathEval("foo(1)")
225: if res != 2:
226: print "xpath extension failure"
227: doc.freeDoc()
228: ctxt.xpathFreeContext()</pre><p>Note how the extension function is registered with the context (but that
229: part 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
230: function 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
240: are not finalized, but it should be sufficient to do contextual work at the
241: evaluation point.</p><h3>Memory debugging:</h3><p>last but not least, all tests starts with the following prologue:</p><pre>#memory debug specific
242: libxml2.debugMemory(1)</pre><p>and ends with the following epilogue:</p><pre>#memory debug specific
243: libxml2.cleanupParser()
244: if libxml2.debugMemory(1) == 0:
245: print "OK"
246: else:
247: print "Memory leak %d bytes" % (libxml2.debugMemory(1))
248: libxml2.dumpMemory()</pre><p>Those activate the memory debugging interface of libxml2 where all
249: allocated block in the library are tracked. The prologue then cleans up the
250: library state and checks that all allocated memory has been freed. If not it
251: calls 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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