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