1:mod:`xml.sax` --- Support for SAX2 parsers 2=========================================== 3 4.. module:: xml.sax 5 :synopsis: Package containing SAX2 base classes and convenience functions. 6 7.. moduleauthor:: Lars Marius Garshol <larsga@garshol.priv.no> 8.. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org> 9.. sectionauthor:: Martin v. Löwis <martin@v.loewis.de> 10 11**Source code:** :source:`Lib/xml/sax/__init__.py` 12 13-------------- 14 15The :mod:`xml.sax` package provides a number of modules which implement the 16Simple API for XML (SAX) interface for Python. The package itself provides the 17SAX exceptions and the convenience functions which will be most used by users of 18the SAX API. 19 20 21.. warning:: 22 23 The :mod:`xml.sax` module is not secure against maliciously 24 constructed data. If you need to parse untrusted or unauthenticated data see 25 :ref:`xml-vulnerabilities`. 26 27.. versionchanged:: 3.7.1 28 29 The SAX parser no longer processes general external entities by default 30 to increase security. Before, the parser created network connections 31 to fetch remote files or loaded local files from the file 32 system for DTD and entities. The feature can be enabled again with method 33 :meth:`~xml.sax.xmlreader.XMLReader.setFeature` on the parser object 34 and argument :data:`~xml.sax.handler.feature_external_ges`. 35 36The convenience functions are: 37 38 39.. function:: make_parser(parser_list=[]) 40 41 Create and return a SAX :class:`~xml.sax.xmlreader.XMLReader` object. The 42 first parser found will 43 be used. If *parser_list* is provided, it must be a list of strings which 44 name modules that have a function named :func:`create_parser`. Modules listed 45 in *parser_list* will be used before modules in the default list of parsers. 46 47 48.. function:: parse(filename_or_stream, handler, error_handler=handler.ErrorHandler()) 49 50 Create a SAX parser and use it to parse a document. The document, passed in as 51 *filename_or_stream*, can be a filename or a file object. The *handler* 52 parameter needs to be a SAX :class:`~handler.ContentHandler` instance. If 53 *error_handler* is given, it must be a SAX :class:`~handler.ErrorHandler` 54 instance; if 55 omitted, :exc:`SAXParseException` will be raised on all errors. There is no 56 return value; all work must be done by the *handler* passed in. 57 58 59.. function:: parseString(string, handler, error_handler=handler.ErrorHandler()) 60 61 Similar to :func:`parse`, but parses from a buffer *string* received as a 62 parameter. *string* must be a :class:`str` instance or a 63 :term:`bytes-like object`. 64 65 .. versionchanged:: 3.5 66 Added support of :class:`str` instances. 67 68A typical SAX application uses three kinds of objects: readers, handlers and 69input sources. "Reader" in this context is another term for parser, i.e. some 70piece of code that reads the bytes or characters from the input source, and 71produces a sequence of events. The events then get distributed to the handler 72objects, i.e. the reader invokes a method on the handler. A SAX application 73must therefore obtain a reader object, create or open the input sources, create 74the handlers, and connect these objects all together. As the final step of 75preparation, the reader is called to parse the input. During parsing, methods on 76the handler objects are called based on structural and syntactic events from the 77input data. 78 79For these objects, only the interfaces are relevant; they are normally not 80instantiated by the application itself. Since Python does not have an explicit 81notion of interface, they are formally introduced as classes, but applications 82may use implementations which do not inherit from the provided classes. The 83:class:`~xml.sax.xmlreader.InputSource`, :class:`~xml.sax.xmlreader.Locator`, 84:class:`~xml.sax.xmlreader.Attributes`, :class:`~xml.sax.xmlreader.AttributesNS`, 85and :class:`~xml.sax.xmlreader.XMLReader` interfaces are defined in the 86module :mod:`xml.sax.xmlreader`. The handler interfaces are defined in 87:mod:`xml.sax.handler`. For convenience, 88:class:`~xml.sax.xmlreader.InputSource` (which is often 89instantiated directly) and the handler classes are also available from 90:mod:`xml.sax`. These interfaces are described below. 91 92In addition to these classes, :mod:`xml.sax` provides the following exception 93classes. 94 95 96.. exception:: SAXException(msg, exception=None) 97 98 Encapsulate an XML error or warning. This class can contain basic error or 99 warning information from either the XML parser or the application: it can be 100 subclassed to provide additional functionality or to add localization. Note 101 that although the handlers defined in the 102 :class:`~xml.sax.handler.ErrorHandler` interface 103 receive instances of this exception, it is not required to actually raise the 104 exception --- it is also useful as a container for information. 105 106 When instantiated, *msg* should be a human-readable description of the error. 107 The optional *exception* parameter, if given, should be ``None`` or an exception 108 that was caught by the parsing code and is being passed along as information. 109 110 This is the base class for the other SAX exception classes. 111 112 113.. exception:: SAXParseException(msg, exception, locator) 114 115 Subclass of :exc:`SAXException` raised on parse errors. Instances of this 116 class are passed to the methods of the SAX 117 :class:`~xml.sax.handler.ErrorHandler` interface to provide information 118 about the parse error. This class supports the SAX 119 :class:`~xml.sax.xmlreader.Locator` interface as well as the 120 :class:`SAXException` interface. 121 122 123.. exception:: SAXNotRecognizedException(msg, exception=None) 124 125 Subclass of :exc:`SAXException` raised when a SAX 126 :class:`~xml.sax.xmlreader.XMLReader` is 127 confronted with an unrecognized feature or property. SAX applications and 128 extensions may use this class for similar purposes. 129 130 131.. exception:: SAXNotSupportedException(msg, exception=None) 132 133 Subclass of :exc:`SAXException` raised when a SAX 134 :class:`~xml.sax.xmlreader.XMLReader` is asked to 135 enable a feature that is not supported, or to set a property to a value that the 136 implementation does not support. SAX applications and extensions may use this 137 class for similar purposes. 138 139 140.. seealso:: 141 142 `SAX: The Simple API for XML <http://www.saxproject.org/>`_ 143 This site is the focal point for the definition of the SAX API. It provides a 144 Java implementation and online documentation. Links to implementations and 145 historical information are also available. 146 147 Module :mod:`xml.sax.handler` 148 Definitions of the interfaces for application-provided objects. 149 150 Module :mod:`xml.sax.saxutils` 151 Convenience functions for use in SAX applications. 152 153 Module :mod:`xml.sax.xmlreader` 154 Definitions of the interfaces for parser-provided objects. 155 156 157.. _sax-exception-objects: 158 159SAXException Objects 160-------------------- 161 162The :class:`SAXException` exception class supports the following methods: 163 164 165.. method:: SAXException.getMessage() 166 167 Return a human-readable message describing the error condition. 168 169 170.. method:: SAXException.getException() 171 172 Return an encapsulated exception object, or ``None``. 173 174