2 :mod:`xmllib` --- A parser for XML documents
3 ============================================
6 :synopsis: A parser for XML documents.
8 .. moduleauthor:: Sjoerd Mullender <Sjoerd.Mullender@cwi.nl>
9 .. sectionauthor:: Sjoerd Mullender <Sjoerd.Mullender@cwi.nl>
14 single: Extensible Markup Language
17 Use :mod:`xml.sax` instead. The newer XML package includes full support for XML
20 .. versionchanged:: 1.5.2
21 Added namespace support.
23 This module defines a class :class:`XMLParser` which serves as the basis for
24 parsing text files formatted in XML (Extensible Markup Language).
27 .. class:: XMLParser()
29 The :class:`XMLParser` class must be instantiated without arguments. [#]_
31 This class provides the following interface methods and instance variables:
34 .. attribute:: XMLParser.attributes
36 A mapping of element names to mappings. The latter mapping maps attribute names
37 that are valid for the element to the default value of the attribute, or if
38 there is no default to ``None``. The default value is the empty dictionary.
39 This variable is meant to be overridden, not extended since the default is
40 shared by all instances of :class:`XMLParser`.
43 .. attribute:: XMLParser.elements
45 A mapping of element names to tuples. The tuples contain a function for
46 handling the start and end tag respectively of the element, or ``None`` if the
47 method :meth:`unknown_starttag` or :meth:`unknown_endtag` is to be called. The
48 default value is the empty dictionary. This variable is meant to be overridden,
49 not extended since the default is shared by all instances of :class:`XMLParser`.
52 .. attribute:: XMLParser.entitydefs
54 A mapping of entitynames to their values. The default value contains
55 definitions for ``'lt'``, ``'gt'``, ``'amp'``, ``'quot'``, and ``'apos'``.
58 .. method:: XMLParser.reset()
60 Reset the instance. Loses all unprocessed data. This is called implicitly at
61 the instantiation time.
64 .. method:: XMLParser.setnomoretags()
66 Stop processing tags. Treat all following input as literal input (CDATA).
69 .. method:: XMLParser.setliteral()
71 Enter literal mode (CDATA mode). This mode is automatically exited when the
72 close tag matching the last unclosed open tag is encountered.
75 .. method:: XMLParser.feed(data)
77 Feed some text to the parser. It is processed insofar as it consists of
78 complete tags; incomplete data is buffered until more data is fed or
79 :meth:`close` is called.
82 .. method:: XMLParser.close()
84 Force processing of all buffered data as if it were followed by an end-of-file
85 mark. This method may be redefined by a derived class to define additional
86 processing at the end of the input, but the redefined version should always call
90 .. method:: XMLParser.translate_references(data)
92 Translate all entity and character references in *data* and return the
96 .. method:: XMLParser.getnamespace()
98 Return a mapping of namespace abbreviations to namespace URIs that are currently
102 .. method:: XMLParser.handle_xml(encoding, standalone)
104 This method is called when the ``<?xml ...?>`` tag is processed. The arguments
105 are the values of the encoding and standalone attributes in the tag. Both
106 encoding and standalone are optional. The values passed to :meth:`handle_xml`
107 default to ``None`` and the string ``'no'`` respectively.
110 .. method:: XMLParser.handle_doctype(tag, pubid, syslit, data)
113 single: DOCTYPE declaration
114 single: Formal Public Identifier
116 This method is called when the ``<!DOCTYPE...>`` declaration is processed. The
117 arguments are the tag name of the root element, the Formal Public Identifier (or
118 ``None`` if not specified), the system identifier, and the uninterpreted
119 contents of the internal DTD subset as a string (or ``None`` if not present).
122 .. method:: XMLParser.handle_starttag(tag, method, attributes)
124 This method is called to handle start tags for which a start tag handler is
125 defined in the instance variable :attr:`elements`. The *tag* argument is the
126 name of the tag, and the *method* argument is the function (method) which should
127 be used to support semantic interpretation of the start tag. The *attributes*
128 argument is a dictionary of attributes, the key being the *name* and the value
129 being the *value* of the attribute found inside the tag's ``<>`` brackets.
130 Character and entity references in the *value* have been interpreted. For
131 instance, for the start tag ``<A HREF="http://www.cwi.nl/">``, this method would
132 be called as ``handle_starttag('A', self.elements['A'][0], {'HREF':
133 'http://www.cwi.nl/'})``. The base implementation simply calls *method* with
134 *attributes* as the only argument.
137 .. method:: XMLParser.handle_endtag(tag, method)
139 This method is called to handle endtags for which an end tag handler is defined
140 in the instance variable :attr:`elements`. The *tag* argument is the name of
141 the tag, and the *method* argument is the function (method) which should be used
142 to support semantic interpretation of the end tag. For instance, for the endtag
143 ``</A>``, this method would be called as ``handle_endtag('A',
144 self.elements['A'][1])``. The base implementation simply calls *method*.
147 .. method:: XMLParser.handle_data(data)
149 This method is called to process arbitrary data. It is intended to be
150 overridden by a derived class; the base class implementation does nothing.
153 .. method:: XMLParser.handle_charref(ref)
155 This method is called to process a character reference of the form ``&#ref;``.
156 *ref* can either be a decimal number, or a hexadecimal number when preceded by
157 an ``'x'``. In the base implementation, *ref* must be a number in the range
158 0-255. It translates the character to ASCII and calls the method
159 :meth:`handle_data` with the character as argument. If *ref* is invalid or out
160 of range, the method ``unknown_charref(ref)`` is called to handle the error. A
161 subclass must override this method to provide support for character references
162 outside of the ASCII range.
165 .. method:: XMLParser.handle_comment(comment)
167 This method is called when a comment is encountered. The *comment* argument is
168 a string containing the text between the ``<!--`` and ``-->`` delimiters, but
169 not the delimiters themselves. For example, the comment ``<!--text-->`` will
170 cause this method to be called with the argument ``'text'``. The default method
174 .. method:: XMLParser.handle_cdata(data)
176 This method is called when a CDATA element is encountered. The *data* argument
177 is a string containing the text between the ``<![CDATA[`` and ``]]>``
178 delimiters, but not the delimiters themselves. For example, the entity
179 ``<![CDATA[text]]>`` will cause this method to be called with the argument
180 ``'text'``. The default method does nothing, and is intended to be overridden.
183 .. method:: XMLParser.handle_proc(name, data)
185 This method is called when a processing instruction (PI) is encountered. The
186 *name* is the PI target, and the *data* argument is a string containing the text
187 between the PI target and the closing delimiter, but not the delimiter itself.
188 For example, the instruction ``<?XML text?>`` will cause this method to be
189 called with the arguments ``'XML'`` and ``'text'``. The default method does
190 nothing. Note that if a document starts with ``<?xml ..?>``, :meth:`handle_xml`
191 is called to handle it.
194 .. method:: XMLParser.handle_special(data)
196 .. index:: single: ENTITY declaration
198 This method is called when a declaration is encountered. The *data* argument is
199 a string containing the text between the ``<!`` and ``>`` delimiters, but not
200 the delimiters themselves. For example, the entity declaration ``<!ENTITY
201 text>`` will cause this method to be called with the argument ``'ENTITY text'``.
202 The default method does nothing. Note that ``<!DOCTYPE ...>`` is handled
203 separately if it is located at the start of the document.
206 .. method:: XMLParser.syntax_error(message)
208 This method is called when a syntax error is encountered. The *message* is a
209 description of what was wrong. The default method raises a :exc:`RuntimeError`
210 exception. If this method is overridden, it is permissible for it to return.
211 This method is only called when the error can be recovered from. Unrecoverable
212 errors raise a :exc:`RuntimeError` without first calling :meth:`syntax_error`.
215 .. method:: XMLParser.unknown_starttag(tag, attributes)
217 This method is called to process an unknown start tag. It is intended to be
218 overridden by a derived class; the base class implementation does nothing.
221 .. method:: XMLParser.unknown_endtag(tag)
223 This method is called to process an unknown end tag. It is intended to be
224 overridden by a derived class; the base class implementation does nothing.
227 .. method:: XMLParser.unknown_charref(ref)
229 This method is called to process unresolvable numeric character references. It
230 is intended to be overridden by a derived class; the base class implementation
234 .. method:: XMLParser.unknown_entityref(ref)
236 This method is called to process an unknown entity reference. It is intended to
237 be overridden by a derived class; the base class implementation calls
238 :meth:`syntax_error` to signal an error.
243 `Extensible Markup Language (XML) 1.0 <http://www.w3.org/TR/REC-xml>`_
244 The XML specification, published by the World Wide Web Consortium (W3C), defines
245 the syntax and processor requirements for XML. References to additional
246 material on XML, including translations of the specification, are available at
247 http://www.w3.org/XML/.
249 `Python and XML Processing <http://www.python.org/topics/xml/>`_
250 The Python XML Topic Guide provides a great deal of information on using XML
251 from Python and links to other sources of information on XML.
253 `SIG for XML Processing in Python <http://www.python.org/sigs/xml-sig/>`_
254 The Python XML Special Interest Group is developing substantial support for
255 processing XML from Python.
263 .. index:: pair: XML; namespaces
265 This module has support for XML namespaces as defined in the XML Namespaces
266 proposed recommendation.
268 Tag and attribute names that are defined in an XML namespace are handled as if
269 the name of the tag or element consisted of the namespace (the URL that defines
270 the namespace) followed by a space and the name of the tag or attribute. For
271 instance, the tag ``<html xmlns='http://www.w3.org/TR/REC-html40'>`` is treated
272 as if the tag name was ``'http://www.w3.org/TR/REC-html40 html'``, and the tag
273 ``<html:a href='http://frob.com'>`` inside the above mentioned element is
274 treated as if the tag name were ``'http://www.w3.org/TR/REC-html40 a'`` and the
275 attribute name as if it were ``'http://www.w3.org/TR/REC-html40 href'``.
277 An older draft of the XML Namespaces proposal is also recognized, but triggers a
283 `Namespaces in XML <http://www.w3.org/TR/REC-xml-names/>`_
284 This World Wide Web Consortium recommendation describes the proper syntax and
285 processing requirements for namespaces in XML.
287 .. rubric:: Footnotes
289 .. [#] Actually, a number of keyword arguments are recognized which influence the
290 parser to accept certain non-standard constructs. The following keyword
291 arguments are currently recognized. The defaults for all of these is ``0``
292 (false) except for the last one for which the default is ``1`` (true).
293 *accept_unquoted_attributes* (accept certain attribute values without requiring
294 quotes), *accept_missing_endtag_name* (accept end tags that look like ``</>``),
295 *map_case* (map upper case to lower case in tags and attributes), *accept_utf8*
296 (allow UTF-8 characters in input; this is required according to the XML
297 standard, but Python does not as yet deal properly with these characters, so
298 this is not the default), *translate_attribute_references* (don't attempt to
299 translate character and entity references in attribute values).