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 an iterable 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 .. versionchanged:: 3.8 48 The *parser_list* argument can be any iterable, not just a list. 49 50 51.. function:: parse(filename_or_stream, handler, error_handler=handler.ErrorHandler()) 52 53 Create a SAX parser and use it to parse a document. The document, passed in as 54 *filename_or_stream*, can be a filename or a file object. The *handler* 55 parameter needs to be a SAX :class:`~handler.ContentHandler` instance. If 56 *error_handler* is given, it must be a SAX :class:`~handler.ErrorHandler` 57 instance; if 58 omitted, :exc:`SAXParseException` will be raised on all errors. There is no 59 return value; all work must be done by the *handler* passed in. 60 61 62.. function:: parseString(string, handler, error_handler=handler.ErrorHandler()) 63 64 Similar to :func:`parse`, but parses from a buffer *string* received as a 65 parameter. *string* must be a :class:`str` instance or a 66 :term:`bytes-like object`. 67 68 .. versionchanged:: 3.5 69 Added support of :class:`str` instances. 70 71A typical SAX application uses three kinds of objects: readers, handlers and 72input sources. "Reader" in this context is another term for parser, i.e. some 73piece of code that reads the bytes or characters from the input source, and 74produces a sequence of events. The events then get distributed to the handler 75objects, i.e. the reader invokes a method on the handler. A SAX application 76must therefore obtain a reader object, create or open the input sources, create 77the handlers, and connect these objects all together. As the final step of 78preparation, the reader is called to parse the input. During parsing, methods on 79the handler objects are called based on structural and syntactic events from the 80input data. 81 82For these objects, only the interfaces are relevant; they are normally not 83instantiated by the application itself. Since Python does not have an explicit 84notion of interface, they are formally introduced as classes, but applications 85may use implementations which do not inherit from the provided classes. The 86:class:`~xml.sax.xmlreader.InputSource`, :class:`~xml.sax.xmlreader.Locator`, 87:class:`~xml.sax.xmlreader.Attributes`, :class:`~xml.sax.xmlreader.AttributesNS`, 88and :class:`~xml.sax.xmlreader.XMLReader` interfaces are defined in the 89module :mod:`xml.sax.xmlreader`. The handler interfaces are defined in 90:mod:`xml.sax.handler`. For convenience, 91:class:`~xml.sax.xmlreader.InputSource` (which is often 92instantiated directly) and the handler classes are also available from 93:mod:`xml.sax`. These interfaces are described below. 94 95In addition to these classes, :mod:`xml.sax` provides the following exception 96classes. 97 98 99.. exception:: SAXException(msg, exception=None) 100 101 Encapsulate an XML error or warning. This class can contain basic error or 102 warning information from either the XML parser or the application: it can be 103 subclassed to provide additional functionality or to add localization. Note 104 that although the handlers defined in the 105 :class:`~xml.sax.handler.ErrorHandler` interface 106 receive instances of this exception, it is not required to actually raise the 107 exception --- it is also useful as a container for information. 108 109 When instantiated, *msg* should be a human-readable description of the error. 110 The optional *exception* parameter, if given, should be ``None`` or an exception 111 that was caught by the parsing code and is being passed along as information. 112 113 This is the base class for the other SAX exception classes. 114 115 116.. exception:: SAXParseException(msg, exception, locator) 117 118 Subclass of :exc:`SAXException` raised on parse errors. Instances of this 119 class are passed to the methods of the SAX 120 :class:`~xml.sax.handler.ErrorHandler` interface to provide information 121 about the parse error. This class supports the SAX 122 :class:`~xml.sax.xmlreader.Locator` interface as well as the 123 :class:`SAXException` interface. 124 125 126.. exception:: SAXNotRecognizedException(msg, exception=None) 127 128 Subclass of :exc:`SAXException` raised when a SAX 129 :class:`~xml.sax.xmlreader.XMLReader` is 130 confronted with an unrecognized feature or property. SAX applications and 131 extensions may use this class for similar purposes. 132 133 134.. exception:: SAXNotSupportedException(msg, exception=None) 135 136 Subclass of :exc:`SAXException` raised when a SAX 137 :class:`~xml.sax.xmlreader.XMLReader` is asked to 138 enable a feature that is not supported, or to set a property to a value that the 139 implementation does not support. SAX applications and extensions may use this 140 class for similar purposes. 141 142 143.. seealso:: 144 145 `SAX: The Simple API for XML <http://www.saxproject.org/>`_ 146 This site is the focal point for the definition of the SAX API. It provides a 147 Java implementation and online documentation. Links to implementations and 148 historical information are also available. 149 150 Module :mod:`xml.sax.handler` 151 Definitions of the interfaces for application-provided objects. 152 153 Module :mod:`xml.sax.saxutils` 154 Convenience functions for use in SAX applications. 155 156 Module :mod:`xml.sax.xmlreader` 157 Definitions of the interfaces for parser-provided objects. 158 159 160.. _sax-exception-objects: 161 162SAXException Objects 163-------------------- 164 165The :class:`SAXException` exception class supports the following methods: 166 167 168.. method:: SAXException.getMessage() 169 170 Return a human-readable message describing the error condition. 171 172 173.. method:: SAXException.getException() 174 175 Return an encapsulated exception object, or ``None``. 176 177