1 :mod:`xml.sax.xmlreader` --- Interface for XML parsers 2 ====================================================== 3 4 .. module:: xml.sax.xmlreader 5 :synopsis: Interface which SAX-compliant XML parsers must implement. 6 7 .. moduleauthor:: Lars Marius Garshol <larsga (a] garshol.priv.no> 8 .. sectionauthor:: Martin v. Lwis <martin (a] v.loewis.de> 9 10 **Source code:** :source:`Lib/xml/sax/xmlreader.py` 11 12 -------------- 13 14 SAX parsers implement the :class:`XMLReader` interface. They are implemented in 15 a Python module, which must provide a function :func:`create_parser`. This 16 function is invoked by :func:`xml.sax.make_parser` with no arguments to create 17 a new parser object. 18 19 20 .. class:: XMLReader() 21 22 Base class which can be inherited by SAX parsers. 23 24 25 .. class:: IncrementalParser() 26 27 In some cases, it is desirable not to parse an input source at once, but to feed 28 chunks of the document as they get available. Note that the reader will normally 29 not read the entire file, but read it in chunks as well; still :meth:`parse` 30 won't return until the entire document is processed. So these interfaces should 31 be used if the blocking behaviour of :meth:`parse` is not desirable. 32 33 When the parser is instantiated it is ready to begin accepting data from the 34 feed method immediately. After parsing has been finished with a call to close 35 the reset method must be called to make the parser ready to accept new data, 36 either from feed or using the parse method. 37 38 Note that these methods must *not* be called during parsing, that is, after 39 parse has been called and before it returns. 40 41 By default, the class also implements the parse method of the XMLReader 42 interface using the feed, close and reset methods of the IncrementalParser 43 interface as a convenience to SAX 2.0 driver writers. 44 45 46 .. class:: Locator() 47 48 Interface for associating a SAX event with a document location. A locator object 49 will return valid results only during calls to DocumentHandler methods; at any 50 other time, the results are unpredictable. If information is not available, 51 methods may return ``None``. 52 53 54 .. class:: InputSource(system_id=None) 55 56 Encapsulation of the information needed by the :class:`XMLReader` to read 57 entities. 58 59 This class may include information about the public identifier, system 60 identifier, byte stream (possibly with character encoding information) and/or 61 the character stream of an entity. 62 63 Applications will create objects of this class for use in the 64 :meth:`XMLReader.parse` method and for returning from 65 EntityResolver.resolveEntity. 66 67 An :class:`InputSource` belongs to the application, the :class:`XMLReader` is 68 not allowed to modify :class:`InputSource` objects passed to it from the 69 application, although it may make copies and modify those. 70 71 72 .. class:: AttributesImpl(attrs) 73 74 This is an implementation of the :class:`Attributes` interface (see section 75 :ref:`attributes-objects`). This is a dictionary-like object which 76 represents the element attributes in a :meth:`startElement` call. In addition 77 to the most useful dictionary operations, it supports a number of other 78 methods as described by the interface. Objects of this class should be 79 instantiated by readers; *attrs* must be a dictionary-like object containing 80 a mapping from attribute names to attribute values. 81 82 83 .. class:: AttributesNSImpl(attrs, qnames) 84 85 Namespace-aware variant of :class:`AttributesImpl`, which will be passed to 86 :meth:`startElementNS`. It is derived from :class:`AttributesImpl`, but 87 understands attribute names as two-tuples of *namespaceURI* and 88 *localname*. In addition, it provides a number of methods expecting qualified 89 names as they appear in the original document. This class implements the 90 :class:`AttributesNS` interface (see section :ref:`attributes-ns-objects`). 91 92 93 .. _xmlreader-objects: 94 95 XMLReader Objects 96 ----------------- 97 98 The :class:`XMLReader` interface supports the following methods: 99 100 101 .. method:: XMLReader.parse(source) 102 103 Process an input source, producing SAX events. The *source* object can be a 104 system identifier (a string identifying the input source -- typically a file 105 name or a URL), a file-like object, or an :class:`InputSource` object. When 106 :meth:`parse` returns, the input is completely processed, and the parser object 107 can be discarded or reset. 108 109 .. versionchanged:: 3.5 110 Added support of character streams. 111 112 113 .. method:: XMLReader.getContentHandler() 114 115 Return the current :class:`~xml.sax.handler.ContentHandler`. 116 117 118 .. method:: XMLReader.setContentHandler(handler) 119 120 Set the current :class:`~xml.sax.handler.ContentHandler`. If no 121 :class:`~xml.sax.handler.ContentHandler` is set, content events will be 122 discarded. 123 124 125 .. method:: XMLReader.getDTDHandler() 126 127 Return the current :class:`~xml.sax.handler.DTDHandler`. 128 129 130 .. method:: XMLReader.setDTDHandler(handler) 131 132 Set the current :class:`~xml.sax.handler.DTDHandler`. If no 133 :class:`~xml.sax.handler.DTDHandler` is set, DTD 134 events will be discarded. 135 136 137 .. method:: XMLReader.getEntityResolver() 138 139 Return the current :class:`~xml.sax.handler.EntityResolver`. 140 141 142 .. method:: XMLReader.setEntityResolver(handler) 143 144 Set the current :class:`~xml.sax.handler.EntityResolver`. If no 145 :class:`~xml.sax.handler.EntityResolver` is set, 146 attempts to resolve an external entity will result in opening the system 147 identifier for the entity, and fail if it is not available. 148 149 150 .. method:: XMLReader.getErrorHandler() 151 152 Return the current :class:`~xml.sax.handler.ErrorHandler`. 153 154 155 .. method:: XMLReader.setErrorHandler(handler) 156 157 Set the current error handler. If no :class:`~xml.sax.handler.ErrorHandler` 158 is set, errors will be raised as exceptions, and warnings will be printed. 159 160 161 .. method:: XMLReader.setLocale(locale) 162 163 Allow an application to set the locale for errors and warnings. 164 165 SAX parsers are not required to provide localization for errors and warnings; if 166 they cannot support the requested locale, however, they must raise a SAX 167 exception. Applications may request a locale change in the middle of a parse. 168 169 170 .. method:: XMLReader.getFeature(featurename) 171 172 Return the current setting for feature *featurename*. If the feature is not 173 recognized, :exc:`SAXNotRecognizedException` is raised. The well-known 174 featurenames are listed in the module :mod:`xml.sax.handler`. 175 176 177 .. method:: XMLReader.setFeature(featurename, value) 178 179 Set the *featurename* to *value*. If the feature is not recognized, 180 :exc:`SAXNotRecognizedException` is raised. If the feature or its setting is not 181 supported by the parser, *SAXNotSupportedException* is raised. 182 183 184 .. method:: XMLReader.getProperty(propertyname) 185 186 Return the current setting for property *propertyname*. If the property is not 187 recognized, a :exc:`SAXNotRecognizedException` is raised. The well-known 188 propertynames are listed in the module :mod:`xml.sax.handler`. 189 190 191 .. method:: XMLReader.setProperty(propertyname, value) 192 193 Set the *propertyname* to *value*. If the property is not recognized, 194 :exc:`SAXNotRecognizedException` is raised. If the property or its setting is 195 not supported by the parser, *SAXNotSupportedException* is raised. 196 197 198 .. _incremental-parser-objects: 199 200 IncrementalParser Objects 201 ------------------------- 202 203 Instances of :class:`IncrementalParser` offer the following additional methods: 204 205 206 .. method:: IncrementalParser.feed(data) 207 208 Process a chunk of *data*. 209 210 211 .. method:: IncrementalParser.close() 212 213 Assume the end of the document. That will check well-formedness conditions that 214 can be checked only at the end, invoke handlers, and may clean up resources 215 allocated during parsing. 216 217 218 .. method:: IncrementalParser.reset() 219 220 This method is called after close has been called to reset the parser so that it 221 is ready to parse new documents. The results of calling parse or feed after 222 close without calling reset are undefined. 223 224 225 .. _locator-objects: 226 227 Locator Objects 228 --------------- 229 230 Instances of :class:`Locator` provide these methods: 231 232 233 .. method:: Locator.getColumnNumber() 234 235 Return the column number where the current event begins. 236 237 238 .. method:: Locator.getLineNumber() 239 240 Return the line number where the current event begins. 241 242 243 .. method:: Locator.getPublicId() 244 245 Return the public identifier for the current event. 246 247 248 .. method:: Locator.getSystemId() 249 250 Return the system identifier for the current event. 251 252 253 .. _input-source-objects: 254 255 InputSource Objects 256 ------------------- 257 258 259 .. method:: InputSource.setPublicId(id) 260 261 Sets the public identifier of this :class:`InputSource`. 262 263 264 .. method:: InputSource.getPublicId() 265 266 Returns the public identifier of this :class:`InputSource`. 267 268 269 .. method:: InputSource.setSystemId(id) 270 271 Sets the system identifier of this :class:`InputSource`. 272 273 274 .. method:: InputSource.getSystemId() 275 276 Returns the system identifier of this :class:`InputSource`. 277 278 279 .. method:: InputSource.setEncoding(encoding) 280 281 Sets the character encoding of this :class:`InputSource`. 282 283 The encoding must be a string acceptable for an XML encoding declaration (see 284 section 4.3.3 of the XML recommendation). 285 286 The encoding attribute of the :class:`InputSource` is ignored if the 287 :class:`InputSource` also contains a character stream. 288 289 290 .. method:: InputSource.getEncoding() 291 292 Get the character encoding of this InputSource. 293 294 295 .. method:: InputSource.setByteStream(bytefile) 296 297 Set the byte stream (a :term:`binary file`) for this input source. 298 299 The SAX parser will ignore this if there is also a character stream specified, 300 but it will use a byte stream in preference to opening a URI connection itself. 301 302 If the application knows the character encoding of the byte stream, it should 303 set it with the setEncoding method. 304 305 306 .. method:: InputSource.getByteStream() 307 308 Get the byte stream for this input source. 309 310 The getEncoding method will return the character encoding for this byte stream, 311 or ``None`` if unknown. 312 313 314 .. method:: InputSource.setCharacterStream(charfile) 315 316 Set the character stream (a :term:`text file`) for this input source. 317 318 If there is a character stream specified, the SAX parser will ignore any byte 319 stream and will not attempt to open a URI connection to the system identifier. 320 321 322 .. method:: InputSource.getCharacterStream() 323 324 Get the character stream for this input source. 325 326 327 .. _attributes-objects: 328 329 The :class:`Attributes` Interface 330 --------------------------------- 331 332 :class:`Attributes` objects implement a portion of the :term:`mapping protocol 333 <mapping>`, including the methods :meth:`~collections.abc.Mapping.copy`, 334 :meth:`~collections.abc.Mapping.get`, :meth:`~object.__contains__`, 335 :meth:`~collections.abc.Mapping.items`, :meth:`~collections.abc.Mapping.keys`, 336 and :meth:`~collections.abc.Mapping.values`. The following methods 337 are also provided: 338 339 340 .. method:: Attributes.getLength() 341 342 Return the number of attributes. 343 344 345 .. method:: Attributes.getNames() 346 347 Return the names of the attributes. 348 349 350 .. method:: Attributes.getType(name) 351 352 Returns the type of the attribute *name*, which is normally ``'CDATA'``. 353 354 355 .. method:: Attributes.getValue(name) 356 357 Return the value of attribute *name*. 358 359 .. getValueByQName, getNameByQName, getQNameByName, getQNames available 360 .. here already, but documented only for derived class. 361 362 363 .. _attributes-ns-objects: 364 365 The :class:`AttributesNS` Interface 366 ----------------------------------- 367 368 This interface is a subtype of the :class:`Attributes` interface (see section 369 :ref:`attributes-objects`). All methods supported by that interface are also 370 available on :class:`AttributesNS` objects. 371 372 The following methods are also available: 373 374 375 .. method:: AttributesNS.getValueByQName(name) 376 377 Return the value for a qualified name. 378 379 380 .. method:: AttributesNS.getNameByQName(name) 381 382 Return the ``(namespace, localname)`` pair for a qualified *name*. 383 384 385 .. method:: AttributesNS.getQNameByName(name) 386 387 Return the qualified name for a ``(namespace, localname)`` pair. 388 389 390 .. method:: AttributesNS.getQNames() 391 392 Return the qualified names of all attributes. 393 394
