144 lines
5.9 KiB
ReStructuredText
144 lines
5.9 KiB
ReStructuredText
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:mod:`xml.sax` --- Support for SAX2 parsers
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===========================================
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.. module:: xml.sax
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:synopsis: Package containing SAX2 base classes and convenience functions.
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.. moduleauthor:: Lars Marius Garshol <larsga@garshol.priv.no>
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.. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org>
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.. sectionauthor:: Martin v. Löwis <martin@v.loewis.de>
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.. versionadded:: 2.0
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The :mod:`xml.sax` package provides a number of modules which implement the
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Simple API for XML (SAX) interface for Python. The package itself provides the
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SAX exceptions and the convenience functions which will be most used by users of
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the SAX API.
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The convenience functions are:
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.. function:: make_parser([parser_list])
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Create and return a SAX :class:`XMLReader` object. The first parser found will
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be used. If *parser_list* is provided, it must be a sequence of strings which
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name modules that have a function named :func:`create_parser`. Modules listed
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in *parser_list* will be used before modules in the default list of parsers.
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.. function:: parse(filename_or_stream, handler[, error_handler])
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Create a SAX parser and use it to parse a document. The document, passed in as
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*filename_or_stream*, can be a filename or a file object. The *handler*
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parameter needs to be a SAX :class:`ContentHandler` instance. If
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*error_handler* is given, it must be a SAX :class:`ErrorHandler` instance; if
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omitted, :exc:`SAXParseException` will be raised on all errors. There is no
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return value; all work must be done by the *handler* passed in.
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.. function:: parseString(string, handler[, error_handler])
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Similar to :func:`parse`, but parses from a buffer *string* received as a
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parameter.
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A typical SAX application uses three kinds of objects: readers, handlers and
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input sources. "Reader" in this context is another term for parser, i.e. some
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piece of code that reads the bytes or characters from the input source, and
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produces a sequence of events. The events then get distributed to the handler
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objects, i.e. the reader invokes a method on the handler. A SAX application
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must therefore obtain a reader object, create or open the input sources, create
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the handlers, and connect these objects all together. As the final step of
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preparation, the reader is called to parse the input. During parsing, methods on
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the handler objects are called based on structural and syntactic events from the
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input data.
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For these objects, only the interfaces are relevant; they are normally not
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instantiated by the application itself. Since Python does not have an explicit
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notion of interface, they are formally introduced as classes, but applications
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may use implementations which do not inherit from the provided classes. The
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:class:`InputSource`, :class:`Locator`, :class:`Attributes`,
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:class:`AttributesNS`, and :class:`XMLReader` interfaces are defined in the
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module :mod:`xml.sax.xmlreader`. The handler interfaces are defined in
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:mod:`xml.sax.handler`. For convenience, :class:`InputSource` (which is often
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instantiated directly) and the handler classes are also available from
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:mod:`xml.sax`. These interfaces are described below.
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In addition to these classes, :mod:`xml.sax` provides the following exception
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classes.
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.. exception:: SAXException(msg[, exception])
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Encapsulate an XML error or warning. This class can contain basic error or
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warning information from either the XML parser or the application: it can be
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subclassed to provide additional functionality or to add localization. Note
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that although the handlers defined in the :class:`ErrorHandler` interface
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receive instances of this exception, it is not required to actually raise the
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exception --- it is also useful as a container for information.
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When instantiated, *msg* should be a human-readable description of the error.
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The optional *exception* parameter, if given, should be ``None`` or an exception
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that was caught by the parsing code and is being passed along as information.
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This is the base class for the other SAX exception classes.
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.. exception:: SAXParseException(msg, exception, locator)
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Subclass of :exc:`SAXException` raised on parse errors. Instances of this class
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are passed to the methods of the SAX :class:`ErrorHandler` interface to provide
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information about the parse error. This class supports the SAX :class:`Locator`
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interface as well as the :class:`SAXException` interface.
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.. exception:: SAXNotRecognizedException(msg[, exception])
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Subclass of :exc:`SAXException` raised when a SAX :class:`XMLReader` is
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confronted with an unrecognized feature or property. SAX applications and
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extensions may use this class for similar purposes.
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.. exception:: SAXNotSupportedException(msg[, exception])
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Subclass of :exc:`SAXException` raised when a SAX :class:`XMLReader` is asked to
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enable a feature that is not supported, or to set a property to a value that the
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implementation does not support. SAX applications and extensions may use this
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class for similar purposes.
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.. seealso::
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`SAX: The Simple API for XML <http://www.saxproject.org/>`_
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This site is the focal point for the definition of the SAX API. It provides a
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Java implementation and online documentation. Links to implementations and
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historical information are also available.
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Module :mod:`xml.sax.handler`
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Definitions of the interfaces for application-provided objects.
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Module :mod:`xml.sax.saxutils`
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Convenience functions for use in SAX applications.
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Module :mod:`xml.sax.xmlreader`
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Definitions of the interfaces for parser-provided objects.
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.. _sax-exception-objects:
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SAXException Objects
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--------------------
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The :class:`SAXException` exception class supports the following methods:
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.. method:: SAXException.getMessage()
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Return a human-readable message describing the error condition.
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.. method:: SAXException.getException()
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Return an encapsulated exception object, or ``None``.
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