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/Doc/library/xml.sax.reader.rst

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  1
  2:mod:`xml.sax.xmlreader` --- Interface for XML parsers
  3======================================================
  4
  5.. module:: xml.sax.xmlreader
  6   :synopsis: Interface which SAX-compliant XML parsers must implement.
  7.. moduleauthor:: Lars Marius Garshol <larsga@garshol.priv.no>
  8.. sectionauthor:: Martin v. Lรถwis <martin@v.loewis.de>
  9
 10
 11.. versionadded:: 2.0
 12
 13SAX parsers implement the :class:`XMLReader` interface. They are implemented in
 14a Python module, which must provide a function :func:`create_parser`. This
 15function is invoked by  :func:`xml.sax.make_parser` with no arguments to create
 16a new  parser object.
 17
 18
 19.. class:: XMLReader()
 20
 21   Base class which can be inherited by SAX parsers.
 22
 23
 24.. class:: IncrementalParser()
 25
 26   In some cases, it is desirable not to parse an input source at once, but to feed
 27   chunks of the document as they get available. Note that the reader will normally
 28   not read the entire file, but read it in chunks as well; still :meth:`parse`
 29   won't return until the entire document is processed. So these interfaces should
 30   be used if the blocking behaviour of :meth:`parse` is not desirable.
 31
 32   When the parser is instantiated it is ready to begin accepting data from the
 33   feed method immediately. After parsing has been finished with a call to close
 34   the reset method must be called to make the parser ready to accept new data,
 35   either from feed or using the parse method.
 36
 37   Note that these methods must *not* be called during parsing, that is, after
 38   parse has been called and before it returns.
 39
 40   By default, the class also implements the parse method of the XMLReader
 41   interface using the feed, close and reset methods of the IncrementalParser
 42   interface as a convenience to SAX 2.0 driver writers.
 43
 44
 45.. class:: Locator()
 46
 47   Interface for associating a SAX event with a document location. A locator object
 48   will return valid results only during calls to DocumentHandler methods; at any
 49   other time, the results are unpredictable. If information is not available,
 50   methods may return ``None``.
 51
 52
 53.. class:: InputSource([systemId])
 54
 55   Encapsulation of the information needed by the :class:`XMLReader` to read
 56   entities.
 57
 58   This class may include information about the public identifier, system
 59   identifier, byte stream (possibly with character encoding information) and/or
 60   the character stream of an entity.
 61
 62   Applications will create objects of this class for use in the
 63   :meth:`XMLReader.parse` method and for returning from
 64   EntityResolver.resolveEntity.
 65
 66   An :class:`InputSource` belongs to the application, the :class:`XMLReader` is
 67   not allowed to modify :class:`InputSource` objects passed to it from the
 68   application, although it may make copies and modify those.
 69
 70
 71.. class:: AttributesImpl(attrs)
 72
 73   This is an implementation of the :class:`Attributes` interface (see section
 74   :ref:`attributes-objects`).  This is a dictionary-like object which
 75   represents the element attributes in a :meth:`startElement` call. In addition
 76   to the most useful dictionary operations, it supports a number of other
 77   methods as described by the interface. Objects of this class should be
 78   instantiated by readers; *attrs* must be a dictionary-like object containing
 79   a mapping from attribute names to attribute values.
 80
 81
 82.. class:: AttributesNSImpl(attrs, qnames)
 83
 84   Namespace-aware variant of :class:`AttributesImpl`, which will be passed to
 85   :meth:`startElementNS`. It is derived from :class:`AttributesImpl`, but
 86   understands attribute names as two-tuples of *namespaceURI* and
 87   *localname*. In addition, it provides a number of methods expecting qualified
 88   names as they appear in the original document.  This class implements the
 89   :class:`AttributesNS` interface (see section :ref:`attributes-ns-objects`).
 90
 91
 92.. _xmlreader-objects:
 93
 94XMLReader Objects
 95-----------------
 96
 97The :class:`XMLReader` interface supports the following methods:
 98
 99
100.. method:: XMLReader.parse(source)
101
102   Process an input source, producing SAX events. The *source* object can be a
103   system identifier (a string identifying the input source -- typically a file
104   name or an URL), a file-like object, or an :class:`InputSource` object. When
105   :meth:`parse` returns, the input is completely processed, and the parser object
106   can be discarded or reset. As a limitation, the current implementation only
107   accepts byte streams; processing of character streams is for further study.
108
109
110.. method:: XMLReader.getContentHandler()
111
112   Return the current :class:`ContentHandler`.
113
114
115.. method:: XMLReader.setContentHandler(handler)
116
117   Set the current :class:`ContentHandler`.  If no :class:`ContentHandler` is set,
118   content events will be discarded.
119
120
121.. method:: XMLReader.getDTDHandler()
122
123   Return the current :class:`DTDHandler`.
124
125
126.. method:: XMLReader.setDTDHandler(handler)
127
128   Set the current :class:`DTDHandler`.  If no :class:`DTDHandler` is set, DTD
129   events will be discarded.
130
131
132.. method:: XMLReader.getEntityResolver()
133
134   Return the current :class:`EntityResolver`.
135
136
137.. method:: XMLReader.setEntityResolver(handler)
138
139   Set the current :class:`EntityResolver`.  If no :class:`EntityResolver` is set,
140   attempts to resolve an external entity will result in opening the system
141   identifier for the entity, and fail if it is not available.
142
143
144.. method:: XMLReader.getErrorHandler()
145
146   Return the current :class:`ErrorHandler`.
147
148
149.. method:: XMLReader.setErrorHandler(handler)
150
151   Set the current error handler.  If no :class:`ErrorHandler` is set, errors will
152   be raised as exceptions, and warnings will be printed.
153
154
155.. method:: XMLReader.setLocale(locale)
156
157   Allow an application to set the locale for errors and warnings.
158
159   SAX parsers are not required to provide localization for errors and warnings; if
160   they cannot support the requested locale, however, they must throw a SAX
161   exception.  Applications may request a locale change in the middle of a parse.
162
163
164.. method:: XMLReader.getFeature(featurename)
165
166   Return the current setting for feature *featurename*.  If the feature is not
167   recognized, :exc:`SAXNotRecognizedException` is raised. The well-known
168   featurenames are listed in the module :mod:`xml.sax.handler`.
169
170
171.. method:: XMLReader.setFeature(featurename, value)
172
173   Set the *featurename* to *value*. If the feature is not recognized,
174   :exc:`SAXNotRecognizedException` is raised. If the feature or its setting is not
175   supported by the parser, *SAXNotSupportedException* is raised.
176
177
178.. method:: XMLReader.getProperty(propertyname)
179
180   Return the current setting for property *propertyname*. If the property is not
181   recognized, a :exc:`SAXNotRecognizedException` is raised. The well-known
182   propertynames are listed in the module :mod:`xml.sax.handler`.
183
184
185.. method:: XMLReader.setProperty(propertyname, value)
186
187   Set the *propertyname* to *value*. If the property is not recognized,
188   :exc:`SAXNotRecognizedException` is raised. If the property or its setting is
189   not supported by the parser, *SAXNotSupportedException* is raised.
190
191
192.. _incremental-parser-objects:
193
194IncrementalParser Objects
195-------------------------
196
197Instances of :class:`IncrementalParser` offer the following additional methods:
198
199
200.. method:: IncrementalParser.feed(data)
201
202   Process a chunk of *data*.
203
204
205.. method:: IncrementalParser.close()
206
207   Assume the end of the document. That will check well-formedness conditions that
208   can be checked only at the end, invoke handlers, and may clean up resources
209   allocated during parsing.
210
211
212.. method:: IncrementalParser.reset()
213
214   This method is called after close has been called to reset the parser so that it
215   is ready to parse new documents. The results of calling parse or feed after
216   close without calling reset are undefined.
217
218
219.. _locator-objects:
220
221Locator Objects
222---------------
223
224Instances of :class:`Locator` provide these methods:
225
226
227.. method:: Locator.getColumnNumber()
228
229   Return the column number where the current event ends.
230
231
232.. method:: Locator.getLineNumber()
233
234   Return the line number where the current event ends.
235
236
237.. method:: Locator.getPublicId()
238
239   Return the public identifier for the current event.
240
241
242.. method:: Locator.getSystemId()
243
244   Return the system identifier for the current event.
245
246
247.. _input-source-objects:
248
249InputSource Objects
250-------------------
251
252
253.. method:: InputSource.setPublicId(id)
254
255   Sets the public identifier of this :class:`InputSource`.
256
257
258.. method:: InputSource.getPublicId()
259
260   Returns the public identifier of this :class:`InputSource`.
261
262
263.. method:: InputSource.setSystemId(id)
264
265   Sets the system identifier of this :class:`InputSource`.
266
267
268.. method:: InputSource.getSystemId()
269
270   Returns the system identifier of this :class:`InputSource`.
271
272
273.. method:: InputSource.setEncoding(encoding)
274
275   Sets the character encoding of this :class:`InputSource`.
276
277   The encoding must be a string acceptable for an XML encoding declaration (see
278   section 4.3.3 of the XML recommendation).
279
280   The encoding attribute of the :class:`InputSource` is ignored if the
281   :class:`InputSource` also contains a character stream.
282
283
284.. method:: InputSource.getEncoding()
285
286   Get the character encoding of this InputSource.
287
288
289.. method:: InputSource.setByteStream(bytefile)
290
291   Set the byte stream (a Python file-like object which does not perform
292   byte-to-character conversion) for this input source.
293
294   The SAX parser will ignore this if there is also a character stream specified,
295   but it will use a byte stream in preference to opening a URI connection itself.
296
297   If the application knows the character encoding of the byte stream, it should
298   set it with the setEncoding method.
299
300
301.. method:: InputSource.getByteStream()
302
303   Get the byte stream for this input source.
304
305   The getEncoding method will return the character encoding for this byte stream,
306   or None if unknown.
307
308
309.. method:: InputSource.setCharacterStream(charfile)
310
311   Set the character stream for this input source. (The stream must be a Python 1.6
312   Unicode-wrapped file-like that performs conversion to Unicode strings.)
313
314   If there is a character stream specified, the SAX parser will ignore any byte
315   stream and will not attempt to open a URI connection to the system identifier.
316
317
318.. method:: InputSource.getCharacterStream()
319
320   Get the character stream for this input source.
321
322
323.. _attributes-objects:
324
325The :class:`Attributes` Interface
326---------------------------------
327
328:class:`Attributes` objects implement a portion of the mapping protocol,
329including the methods :meth:`copy`, :meth:`get`, :meth:`has_key`, :meth:`items`,
330:meth:`keys`, and :meth:`values`.  The following methods are also provided:
331
332
333.. method:: Attributes.getLength()
334
335   Return the number of attributes.
336
337
338.. method:: Attributes.getNames()
339
340   Return the names of the attributes.
341
342
343.. method:: Attributes.getType(name)
344
345   Returns the type of the attribute *name*, which is normally ``'CDATA'``.
346
347
348.. method:: Attributes.getValue(name)
349
350   Return the value of attribute *name*.
351
352.. getValueByQName, getNameByQName, getQNameByName, getQNames available
353.. here already, but documented only for derived class.
354
355
356.. _attributes-ns-objects:
357
358The :class:`AttributesNS` Interface
359-----------------------------------
360
361This interface is a subtype of the :class:`Attributes` interface (see section
362:ref:`attributes-objects`).  All methods supported by that interface are also
363available on :class:`AttributesNS` objects.
364
365The following methods are also available:
366
367
368.. method:: AttributesNS.getValueByQName(name)
369
370   Return the value for a qualified name.
371
372
373.. method:: AttributesNS.getNameByQName(name)
374
375   Return the ``(namespace, localname)`` pair for a qualified *name*.
376
377
378.. method:: AttributesNS.getQNameByName(name)
379
380   Return the qualified name for a ``(namespace, localname)`` pair.
381
382
383.. method:: AttributesNS.getQNames()
384
385   Return the qualified names of all attributes.
386