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

===========================================

.. module:: xml.sax

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

.. moduleauthor:: Lars Marius Garshol <larsga@garshol.priv.no>

.. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org>

.. sectionauthor:: Martin v. Löwis <martin@v.loewis.de>

.. versionadded:: 2.0

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

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

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

the SAX API.

The convenience functions are:

.. function:: make_parser([parser_list])

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

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

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

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

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

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

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

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

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

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

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

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

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

   parameter.

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

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

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

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

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

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

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

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

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

input data.

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

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

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

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

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

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

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

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

instantiated directly) and the handler classes are also available from

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

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

classes.

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

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

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

   subclassed to provide additional functionality or to add localization.  Note

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

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

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

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

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

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

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

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

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

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

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

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

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

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

   confronted with an unrecognized feature or property.  SAX applications and

   extensions may use this class for similar purposes.

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

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

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

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

   class for similar purposes.

.. seealso::

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

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

      Java implementation and online documentation.  Links to implementations and

      historical information are also available.

   Module :mod:`xml.sax.handler`

      Definitions of the interfaces for application-provided objects.

   Module :mod:`xml.sax.saxutils`

      Convenience functions for use in SAX applications.

   Module :mod:`xml.sax.xmlreader`

      Definitions of the interfaces for parser-provided objects.

.. _sax-exception-objects:

SAXException Objects

--------------------

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

.. method:: SAXException.getMessage()

   Return a human-readable message describing the error condition.

.. method:: SAXException.getException()

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