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. Löwis <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 a 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:`~xml.sax.handler.ContentHandler`. 113 114 115.. method:: XMLReader.setContentHandler(handler) 116 117 Set the current :class:`~xml.sax.handler.ContentHandler`. If no 118 :class:`~xml.sax.handler.ContentHandler` is set, content events will be 119 discarded. 120 121 122.. method:: XMLReader.getDTDHandler() 123 124 Return the current :class:`~xml.sax.handler.DTDHandler`. 125 126 127.. method:: XMLReader.setDTDHandler(handler) 128 129 Set the current :class:`~xml.sax.handler.DTDHandler`. If no 130 :class:`~xml.sax.handler.DTDHandler` is set, DTD 131 events will be discarded. 132 133 134.. method:: XMLReader.getEntityResolver() 135 136 Return the current :class:`~xml.sax.handler.EntityResolver`. 137 138 139.. method:: XMLReader.setEntityResolver(handler) 140 141 Set the current :class:`~xml.sax.handler.EntityResolver`. If no 142 :class:`~xml.sax.handler.EntityResolver` is set, 143 attempts to resolve an external entity will result in opening the system 144 identifier for the entity, and fail if it is not available. 145 146 147.. method:: XMLReader.getErrorHandler() 148 149 Return the current :class:`~xml.sax.handler.ErrorHandler`. 150 151 152.. method:: XMLReader.setErrorHandler(handler) 153 154 Set the current error handler. If no :class:`~xml.sax.handler.ErrorHandler` 155 is set, errors will be raised as exceptions, and warnings will be printed. 156 157 158.. method:: XMLReader.setLocale(locale) 159 160 Allow an application to set the locale for errors and warnings. 161 162 SAX parsers are not required to provide localization for errors and warnings; if 163 they cannot support the requested locale, however, they must raise a SAX 164 exception. Applications may request a locale change in the middle of a parse. 165 166 167.. method:: XMLReader.getFeature(featurename) 168 169 Return the current setting for feature *featurename*. If the feature is not 170 recognized, :exc:`SAXNotRecognizedException` is raised. The well-known 171 featurenames are listed in the module :mod:`xml.sax.handler`. 172 173 174.. method:: XMLReader.setFeature(featurename, value) 175 176 Set the *featurename* to *value*. If the feature is not recognized, 177 :exc:`SAXNotRecognizedException` is raised. If the feature or its setting is not 178 supported by the parser, *SAXNotSupportedException* is raised. 179 180 181.. method:: XMLReader.getProperty(propertyname) 182 183 Return the current setting for property *propertyname*. If the property is not 184 recognized, a :exc:`SAXNotRecognizedException` is raised. The well-known 185 propertynames are listed in the module :mod:`xml.sax.handler`. 186 187 188.. method:: XMLReader.setProperty(propertyname, value) 189 190 Set the *propertyname* to *value*. If the property is not recognized, 191 :exc:`SAXNotRecognizedException` is raised. If the property or its setting is 192 not supported by the parser, *SAXNotSupportedException* is raised. 193 194 195.. _incremental-parser-objects: 196 197IncrementalParser Objects 198------------------------- 199 200Instances of :class:`IncrementalParser` offer the following additional methods: 201 202 203.. method:: IncrementalParser.feed(data) 204 205 Process a chunk of *data*. 206 207 208.. method:: IncrementalParser.close() 209 210 Assume the end of the document. That will check well-formedness conditions that 211 can be checked only at the end, invoke handlers, and may clean up resources 212 allocated during parsing. 213 214 215.. method:: IncrementalParser.reset() 216 217 This method is called after close has been called to reset the parser so that it 218 is ready to parse new documents. The results of calling parse or feed after 219 close without calling reset are undefined. 220 221 222.. _locator-objects: 223 224Locator Objects 225--------------- 226 227Instances of :class:`Locator` provide these methods: 228 229 230.. method:: Locator.getColumnNumber() 231 232 Return the column number where the current event begins. 233 234 235.. method:: Locator.getLineNumber() 236 237 Return the line number where the current event begins. 238 239 240.. method:: Locator.getPublicId() 241 242 Return the public identifier for the current event. 243 244 245.. method:: Locator.getSystemId() 246 247 Return the system identifier for the current event. 248 249 250.. _input-source-objects: 251 252InputSource Objects 253------------------- 254 255 256.. method:: InputSource.setPublicId(id) 257 258 Sets the public identifier of this :class:`InputSource`. 259 260 261.. method:: InputSource.getPublicId() 262 263 Returns the public identifier of this :class:`InputSource`. 264 265 266.. method:: InputSource.setSystemId(id) 267 268 Sets the system identifier of this :class:`InputSource`. 269 270 271.. method:: InputSource.getSystemId() 272 273 Returns the system identifier of this :class:`InputSource`. 274 275 276.. method:: InputSource.setEncoding(encoding) 277 278 Sets the character encoding of this :class:`InputSource`. 279 280 The encoding must be a string acceptable for an XML encoding declaration (see 281 section 4.3.3 of the XML recommendation). 282 283 The encoding attribute of the :class:`InputSource` is ignored if the 284 :class:`InputSource` also contains a character stream. 285 286 287.. method:: InputSource.getEncoding() 288 289 Get the character encoding of this InputSource. 290 291 292.. method:: InputSource.setByteStream(bytefile) 293 294 Set the byte stream (a Python file-like object which does not perform 295 byte-to-character conversion) for this input source. 296 297 The SAX parser will ignore this if there is also a character stream specified, 298 but it will use a byte stream in preference to opening a URI connection itself. 299 300 If the application knows the character encoding of the byte stream, it should 301 set it with the setEncoding method. 302 303 304.. method:: InputSource.getByteStream() 305 306 Get the byte stream for this input source. 307 308 The getEncoding method will return the character encoding for this byte stream, 309 or ``None`` if unknown. 310 311 312.. method:: InputSource.setCharacterStream(charfile) 313 314 Set the character stream for this input source. (The stream must be a Python 1.6 315 Unicode-wrapped file-like that performs conversion to Unicode strings.) 316 317 If there is a character stream specified, the SAX parser will ignore any byte 318 stream and will not attempt to open a URI connection to the system identifier. 319 320 321.. method:: InputSource.getCharacterStream() 322 323 Get the character stream for this input source. 324 325 326.. _attributes-objects: 327 328The :class:`Attributes` Interface 329--------------------------------- 330 331:class:`Attributes` objects implement a portion of the mapping protocol, 332including the methods :meth:`~collections.Mapping.copy`, 333:meth:`~collections.Mapping.get`, 334:meth:`~collections.Mapping.has_key`, 335:meth:`~collections.Mapping.items`, 336:meth:`~collections.Mapping.keys`, 337and :meth:`~collections.Mapping.values`. The following methods 338are also provided: 339 340 341.. method:: Attributes.getLength() 342 343 Return the number of attributes. 344 345 346.. method:: Attributes.getNames() 347 348 Return the names of the attributes. 349 350 351.. method:: Attributes.getType(name) 352 353 Returns the type of the attribute *name*, which is normally ``'CDATA'``. 354 355 356.. method:: Attributes.getValue(name) 357 358 Return the value of attribute *name*. 359 360.. getValueByQName, getNameByQName, getQNameByName, getQNames available 361.. here already, but documented only for derived class. 362 363 364.. _attributes-ns-objects: 365 366The :class:`AttributesNS` Interface 367----------------------------------- 368 369This interface is a subtype of the :class:`Attributes` interface (see section 370:ref:`attributes-objects`). All methods supported by that interface are also 371available on :class:`AttributesNS` objects. 372 373The following methods are also available: 374 375 376.. method:: AttributesNS.getValueByQName(name) 377 378 Return the value for a qualified name. 379 380 381.. method:: AttributesNS.getNameByQName(name) 382 383 Return the ``(namespace, localname)`` pair for a qualified *name*. 384 385 386.. method:: AttributesNS.getQNameByName(name) 387 388 Return the qualified name for a ``(namespace, localname)`` pair. 389 390 391.. method:: AttributesNS.getQNames() 392 393 Return the qualified names of all attributes. 394 395