1 

     2 :mod:`xml.sax` --- Support for SAX2 parsers

     3 ===========================================

     4 

     5 .. module:: xml.sax

     6    :synopsis: Package containing SAX2 base classes and convenience functions.

     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 

    12 .. versionadded:: 2.0

    13 

    14 The :mod:`xml.sax` package provides a number of modules which implement the

    15 Simple API for XML (SAX) interface for Python.  The package itself provides the

    16 SAX exceptions and the convenience functions which will be most used by users of

    17 the SAX API.

    18 

    19 The convenience functions are:

    20 

    21 

    22 .. function:: make_parser([parser_list])

    23 

    24    Create and return a SAX :class:`XMLReader` object.  The first parser found will

    25    be used.  If *parser_list* is provided, it must be a sequence of strings which

    26    name modules that have a function named :func:`create_parser`.  Modules listed

    27    in *parser_list* will be used before modules in the default list of parsers.

    28 

    29 

    30 .. function:: parse(filename_or_stream, handler[, error_handler])

    31 

    32    Create a SAX parser and use it to parse a document.  The document, passed in as

    33    *filename_or_stream*, can be a filename or a file object.  The *handler*

    34    parameter needs to be a SAX :class:`ContentHandler` instance.  If

    35    *error_handler* is given, it must be a SAX :class:`ErrorHandler` instance; if

    36    omitted,  :exc:`SAXParseException` will be raised on all errors.  There is no

    37    return value; all work must be done by the *handler* passed in.

    38 

    39 

    40 .. function:: parseString(string, handler[, error_handler])

    41 

    42    Similar to :func:`parse`, but parses from a buffer *string* received as a

    43    parameter.

    44 

    45 A typical SAX application uses three kinds of objects: readers, handlers and

    46 input sources.  "Reader" in this context is another term for parser, i.e. some

    47 piece of code that reads the bytes or characters from the input source, and

    48 produces a sequence of events. The events then get distributed to the handler

    49 objects, i.e. the reader invokes a method on the handler.  A SAX application

    50 must therefore obtain a reader object, create or open the input sources, create

    51 the handlers, and connect these objects all together.  As the final step of

    52 preparation, the reader is called to parse the input. During parsing, methods on

    53 the handler objects are called based on structural and syntactic events from the

    54 input data.

    55 

    56 For these objects, only the interfaces are relevant; they are normally not

    57 instantiated by the application itself.  Since Python does not have an explicit

    58 notion of interface, they are formally introduced as classes, but applications

    59 may use implementations which do not inherit from the provided classes.  The

    60 :class:`InputSource`, :class:`Locator`, :class:`Attributes`,

    61 :class:`AttributesNS`, and :class:`XMLReader` interfaces are defined in the

    62 module :mod:`xml.sax.xmlreader`.  The handler interfaces are defined in

    63 :mod:`xml.sax.handler`.  For convenience, :class:`InputSource` (which is often

    64 instantiated directly) and the handler classes are also available from

    65 :mod:`xml.sax`.  These interfaces are described below.

    66 

    67 In addition to these classes, :mod:`xml.sax` provides the following exception

    68 classes.

    69 

    70 

    71 .. exception:: SAXException(msg[, exception])

    72 

    73    Encapsulate an XML error or warning.  This class can contain basic error or

    74    warning information from either the XML parser or the application: it can be

    75    subclassed to provide additional functionality or to add localization.  Note

    76    that although the handlers defined in the :class:`ErrorHandler` interface

    77    receive instances of this exception, it is not required to actually raise the

    78    exception --- it is also useful as a container for information.

    79 

    80    When instantiated, *msg* should be a human-readable description of the error.

    81    The optional *exception* parameter, if given, should be ``None`` or an exception

    82    that was caught by the parsing code and is being passed along as information.

    83 

    84    This is the base class for the other SAX exception classes.

    85 

    86 

    87 .. exception:: SAXParseException(msg, exception, locator)

    88 

    89    Subclass of :exc:`SAXException` raised on parse errors. Instances of this class

    90    are passed to the methods of the SAX :class:`ErrorHandler` interface to provide

    91    information about the parse error.  This class supports the SAX :class:`Locator`

    92    interface as well as the :class:`SAXException` interface.

    93 

    94 

    95 .. exception:: SAXNotRecognizedException(msg[, exception])

    96 

    97    Subclass of :exc:`SAXException` raised when a SAX :class:`XMLReader` is

    98    confronted with an unrecognized feature or property.  SAX applications and

    99    extensions may use this class for similar purposes.

   100 

   101 

   102 .. exception:: SAXNotSupportedException(msg[, exception])

   103 

   104    Subclass of :exc:`SAXException` raised when a SAX :class:`XMLReader` is asked to

   105    enable a feature that is not supported, or to set a property to a value that the

   106    implementation does not support.  SAX applications and extensions may use this

   107    class for similar purposes.

   108 

   109 

   110 .. seealso::

   111 

   112    `SAX: The Simple API for XML <http://www.saxproject.org/>`_

   113       This site is the focal point for the definition of the SAX API.  It provides a

   114       Java implementation and online documentation.  Links to implementations and

   115       historical information are also available.

   116 

   117    Module :mod:`xml.sax.handler`

   118       Definitions of the interfaces for application-provided objects.

   119 

   120    Module :mod:`xml.sax.saxutils`

   121       Convenience functions for use in SAX applications.

   122 

   123    Module :mod:`xml.sax.xmlreader`

   124       Definitions of the interfaces for parser-provided objects.

   125 

   126 

   127 .. _sax-exception-objects:

   128 

   129 SAXException Objects

   130 --------------------

   131 

   132 The :class:`SAXException` exception class supports the following methods:

   133 

   134 

   135 .. method:: SAXException.getMessage()

   136 

   137    Return a human-readable message describing the error condition.

   138 

   139 

   140 .. method:: SAXException.getException()

   141 

   142    Return an encapsulated exception object, or ``None``.

   143