
``xml.sax`` --- Support for SAX2 parsers
****************************************

The ``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:

xml.sax.make_parser(parser_list=[])

   Create and return a SAX ``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
   ``create_parser()``.  Modules listed in *parser_list* will be used
   before modules in the default list of parsers.

xml.sax.parse(filename_or_stream, handler, error_handler=handler.ErrorHandler())

   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
   ``ContentHandler`` instance.  If *error_handler* is given, it must
   be a SAX ``ErrorHandler`` instance; if omitted,
   ``SAXParseException`` will be raised on all errors.  There is no
   return value; all work must be done by the *handler* passed in.

xml.sax.parseString(string, handler, error_handler=handler.ErrorHandler())

   Similar to ``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 ``InputSource``, ``Locator``,
``Attributes``, ``AttributesNS``, and ``XMLReader`` interfaces are
defined in the module ``xml.sax.xmlreader``.  The handler interfaces
are defined in ``xml.sax.handler``.  For convenience, ``InputSource``
(which is often instantiated directly) and the handler classes are
also available from ``xml.sax``.  These interfaces are described
below.

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

exception exception xml.sax.SAXException(msg, exception=None)

   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 ``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 exception xml.sax.SAXParseException(msg, exception, locator)

   Subclass of ``SAXException`` raised on parse errors. Instances of
   this class are passed to the methods of the SAX ``ErrorHandler``
   interface to provide information about the parse error.  This class
   supports the SAX ``Locator`` interface as well as the
   ``SAXException`` interface.

exception exception xml.sax.SAXNotRecognizedException(msg, exception=None)

   Subclass of ``SAXException`` raised when a SAX ``XMLReader`` is
   confronted with an unrecognized feature or property.  SAX
   applications and extensions may use this class for similar
   purposes.

exception exception xml.sax.SAXNotSupportedException(msg, exception=None)

   Subclass of ``SAXException`` raised when a SAX ``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.

See also:

   SAX: The Simple API for XML
      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 ``xml.sax.handler``
      Definitions of the interfaces for application-provided objects.

   Module ``xml.sax.saxutils``
      Convenience functions for use in SAX applications.

   Module ``xml.sax.xmlreader``
      Definitions of the interfaces for parser-provided objects.


SAXException Objects
====================

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

SAXException.getMessage()

   Return a human-readable message describing the error condition.

SAXException.getException()

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