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c5e2792ab4
Add hyperlinks to make the documentation on the Attributes and AttributesNS interfaces more discoverable. Closes SF bug #484603.
352 lines
13 KiB
TeX
352 lines
13 KiB
TeX
\section{\module{xml.sax.xmlreader} ---
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Interface for XML parsers}
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\declaremodule{standard}{xml.sax.xmlreader}
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\modulesynopsis{Interface which SAX-compliant XML parsers must implement.}
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\sectionauthor{Martin v. L\"owis}{loewis@informatik.hu-berlin.de}
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\moduleauthor{Lars Marius Garshol}{larsga@garshol.priv.no}
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\versionadded{2.0}
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SAX parsers implement the \class{XMLReader} interface. They are
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implemented in a Python module, which must provide a function
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\function{create_parser()}. This function is invoked by
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\function{xml.sax.make_parser()} with no arguments to create a new
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parser object.
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\begin{classdesc}{XMLReader}{}
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Base class which can be inherited by SAX parsers.
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\end{classdesc}
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\begin{classdesc}{IncrementalParser}{}
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In some cases, it is desirable not to parse an input source at once,
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but to feed chunks of the document as they get available. Note that
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the reader will normally not read the entire file, but read it in
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chunks as well; still \method{parse()} won't return until the entire
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document is processed. So these interfaces should be used if the
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blocking behaviour of \method{parse()} is not desirable.
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When the parser is instantiated it is ready to begin accepting data
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from the feed method immediately. After parsing has been finished
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with a call to close the reset method must be called to make the
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parser ready to accept new data, either from feed or using the parse
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method.
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Note that these methods must \emph{not} be called during parsing,
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that is, after parse has been called and before it returns.
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By default, the class also implements the parse method of the
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XMLReader interface using the feed, close and reset methods of the
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IncrementalParser interface as a convenience to SAX 2.0 driver
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writers.
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\end{classdesc}
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\begin{classdesc}{Locator}{}
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Interface for associating a SAX event with a document location. A
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locator object will return valid results only during calls to
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DocumentHandler methods; at any other time, the results are
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unpredictable. If information is not available, methods may return
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\code{None}.
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\end{classdesc}
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\begin{classdesc}{InputSource}{\optional{systemId}}
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Encapsulation of the information needed by the \class{XMLReader} to
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read entities.
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This class may include information about the public identifier,
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system identifier, byte stream (possibly with character encoding
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information) and/or the character stream of an entity.
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Applications will create objects of this class for use in the
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\method{XMLReader.parse()} method and for returning from
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EntityResolver.resolveEntity.
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An \class{InputSource} belongs to the application, the
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\class{XMLReader} is not allowed to modify \class{InputSource} objects
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passed to it from the application, although it may make copies and
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modify those.
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\end{classdesc}
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\begin{classdesc}{AttributesImpl}{attrs}
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This is an implementation of the \ulink{\class{Attributes}
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interface}{attributes-objects.html} (see
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section~\ref{attributes-objects}). This is a dictionary-like
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object which represents the element attributes in a
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\method{startElement()} call. In addition to the most useful
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dictionary operations, it supports a number of other methods as
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described by the interface. Objects of this class should be
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instantiated by readers; \var{attrs} must be a dictionary-like
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object containing a mapping from attribute names to attribute
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values.
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\end{classdesc}
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\begin{classdesc}{AttributesNSImpl}{attrs, qnames}
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Namespace-aware variant of \class{AttributesImpl}, which will be
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passed to \method{startElementNS()}. It is derived from
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\class{AttributesImpl}, but understands attribute names as
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two-tuples of \var{namespaceURI} and \var{localname}. In addition,
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it provides a number of methods expecting qualified names as they
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appear in the original document. This class implements the
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\ulink{\class{AttributesNS} interface}{attributes-ns-objects.html}
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(see section~\ref{attributes-ns-objects}).
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\end{classdesc}
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\subsection{XMLReader Objects \label{xmlreader-objects}}
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The \class{XMLReader} interface supports the following methods:
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\begin{methoddesc}[XMLReader]{parse}{source}
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Process an input source, producing SAX events. The \var{source}
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object can be a system identifier (a string identifying the
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input source -- typically a file name or an URL), a file-like
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object, or an \class{InputSource} object. When \method{parse()}
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returns, the input is completely processed, and the parser object
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can be discarded or reset. As a limitation, the current implementation
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only accepts byte streams; processing of character streams is for
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further study.
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\end{methoddesc}
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\begin{methoddesc}[XMLReader]{getContentHandler}{}
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Return the current \class{ContentHandler}.
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\end{methoddesc}
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\begin{methoddesc}[XMLReader]{setContentHandler}{handler}
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Set the current \class{ContentHandler}. If no
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\class{ContentHandler} is set, content events will be discarded.
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\end{methoddesc}
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\begin{methoddesc}[XMLReader]{getDTDHandler}{}
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Return the current \class{DTDHandler}.
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\end{methoddesc}
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\begin{methoddesc}[XMLReader]{setDTDHandler}{handler}
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Set the current \class{DTDHandler}. If no \class{DTDHandler} is
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set, DTD events will be discarded.
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\end{methoddesc}
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\begin{methoddesc}[XMLReader]{getEntityResolver}{}
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Return the current \class{EntityResolver}.
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\end{methoddesc}
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\begin{methoddesc}[XMLReader]{setEntityResolver}{handler}
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Set the current \class{EntityResolver}. If no
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\class{EntityResolver} is set, attempts to resolve an external
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entity will result in opening the system identifier for the entity,
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and fail if it is not available.
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\end{methoddesc}
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\begin{methoddesc}[XMLReader]{getErrorHandler}{}
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Return the current \class{ErrorHandler}.
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\end{methoddesc}
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\begin{methoddesc}[XMLReader]{setErrorHandler}{handler}
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Set the current error handler. If no \class{ErrorHandler} is set,
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errors will be raised as exceptions, and warnings will be printed.
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\end{methoddesc}
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\begin{methoddesc}[XMLReader]{setLocale}{locale}
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Allow an application to set the locale for errors and warnings.
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SAX parsers are not required to provide localization for errors and
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warnings; if they cannot support the requested locale, however, they
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must throw a SAX exception. Applications may request a locale change
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in the middle of a parse.
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\end{methoddesc}
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\begin{methoddesc}[XMLReader]{getFeature}{featurename}
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Return the current setting for feature \var{featurename}. If the
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feature is not recognized, \exception{SAXNotRecognizedException} is
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raised. The well-known featurenames are listed in the module
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\module{xml.sax.handler}.
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\end{methoddesc}
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\begin{methoddesc}[XMLReader]{setFeature}{featurename, value}
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Set the \var{featurename} to \var{value}. If the feature is not
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recognized, \exception{SAXNotRecognizedException} is raised. If the
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feature or its setting is not supported by the parser,
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\var{SAXNotSupportedException} is raised.
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\end{methoddesc}
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\begin{methoddesc}[XMLReader]{getProperty}{propertyname}
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Return the current setting for property \var{propertyname}. If the
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property is not recognized, a \exception{SAXNotRecognizedException}
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is raised. The well-known propertynames are listed in the module
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\module{xml.sax.handler}.
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\end{methoddesc}
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\begin{methoddesc}[XMLReader]{setProperty}{propertyname, value}
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Set the \var{propertyname} to \var{value}. If the property is not
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recognized, \exception{SAXNotRecognizedException} is raised. If the
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property or its setting is not supported by the parser,
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\var{SAXNotSupportedException} is raised.
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\end{methoddesc}
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\subsection{IncrementalParser Objects
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\label{incremental-parser-objects}}
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Instances of \class{IncrementalParser} offer the following additional
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methods:
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\begin{methoddesc}[IncrementalParser]{feed}{data}
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Process a chunk of \var{data}.
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\end{methoddesc}
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\begin{methoddesc}[IncrementalParser]{close}{}
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Assume the end of the document. That will check well-formedness
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conditions that can be checked only at the end, invoke handlers, and
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may clean up resources allocated during parsing.
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\end{methoddesc}
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\begin{methoddesc}[IncrementalParser]{reset}{}
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This method is called after close has been called to reset the
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parser so that it is ready to parse new documents. The results of
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calling parse or feed after close without calling reset are
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undefined.
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\end{methoddesc}
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\subsection{Locator Objects \label{locator-objects}}
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Instances of \class{Locator} provide these methods:
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\begin{methoddesc}[Locator]{getColumnNumber}{}
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Return the column number where the current event ends.
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\end{methoddesc}
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\begin{methoddesc}[Locator]{getLineNumber}{}
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Return the line number where the current event ends.
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\end{methoddesc}
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\begin{methoddesc}[Locator]{getPublicId}{}
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Return the public identifier for the current event.
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\end{methoddesc}
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\begin{methoddesc}[Locator]{getSystemId}{}
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Return the system identifier for the current event.
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\end{methoddesc}
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\subsection{InputSource Objects \label{input-source-objects}}
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\begin{methoddesc}[InputSource]{setPublicId}{id}
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Sets the public identifier of this \class{InputSource}.
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\end{methoddesc}
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\begin{methoddesc}[InputSource]{getPublicId}{}
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Returns the public identifier of this \class{InputSource}.
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\end{methoddesc}
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\begin{methoddesc}[InputSource]{setSystemId}{id}
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Sets the system identifier of this \class{InputSource}.
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\end{methoddesc}
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\begin{methoddesc}[InputSource]{getSystemId}{}
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Returns the system identifier of this \class{InputSource}.
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\end{methoddesc}
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\begin{methoddesc}[InputSource]{setEncoding}{encoding}
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Sets the character encoding of this \class{InputSource}.
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The encoding must be a string acceptable for an XML encoding
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declaration (see section 4.3.3 of the XML recommendation).
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The encoding attribute of the \class{InputSource} is ignored if the
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\class{InputSource} also contains a character stream.
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\end{methoddesc}
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\begin{methoddesc}[InputSource]{getEncoding}{}
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Get the character encoding of this InputSource.
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\end{methoddesc}
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\begin{methoddesc}[InputSource]{setByteStream}{bytefile}
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Set the byte stream (a Python file-like object which does not
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perform byte-to-character conversion) for this input source.
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The SAX parser will ignore this if there is also a character stream
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specified, but it will use a byte stream in preference to opening a
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URI connection itself.
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If the application knows the character encoding of the byte stream,
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it should set it with the setEncoding method.
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\end{methoddesc}
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\begin{methoddesc}[InputSource]{getByteStream}{}
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Get the byte stream for this input source.
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The getEncoding method will return the character encoding for this
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byte stream, or None if unknown.
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\end{methoddesc}
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\begin{methoddesc}[InputSource]{setCharacterStream}{charfile}
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Set the character stream for this input source. (The stream must be
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a Python 1.6 Unicode-wrapped file-like that performs conversion to
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Unicode strings.)
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If there is a character stream specified, the SAX parser will ignore
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any byte stream and will not attempt to open a URI connection to the
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system identifier.
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\end{methoddesc}
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\begin{methoddesc}[InputSource]{getCharacterStream}{}
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Get the character stream for this input source.
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\end{methoddesc}
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\subsection{The \class{Attributes} Interface \label{attributes-objects}}
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\class{Attributes} objects implement a portion of the mapping
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protocol, including the methods \method{copy()}, \method{get()},
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\method{has_key()}, \method{items()}, \method{keys()}, and
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\method{values()}. The following methods are also provided:
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\begin{methoddesc}[Attributes]{getLength}{}
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Return the number of attributes.
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\end{methoddesc}
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\begin{methoddesc}[Attributes]{getNames}{}
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Return the names of the attributes.
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\end{methoddesc}
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\begin{methoddesc}[Attributes]{getType}{name}
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Returns the type of the attribute \var{name}, which is normally
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\code{'CDATA'}.
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\end{methoddesc}
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\begin{methoddesc}[Attributes]{getValue}{name}
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Return the value of attribute \var{name}.
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\end{methoddesc}
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% getValueByQName, getNameByQName, getQNameByName, getQNames available
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% here already, but documented only for derived class.
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\subsection{The \class{AttributesNS} Interface \label{attributes-ns-objects}}
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This interface is a subtype of the \ulink{\class{Attributes}
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interface}{attributes-objects.html} (see
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section~\ref{attributes-objects}). All methods supported by that
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interface are also available on \class{AttributesNS} objects.
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The following methods are also available:
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\begin{methoddesc}[AttributesNS]{getValueByQName}{name}
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Return the value for a qualified name.
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\end{methoddesc}
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\begin{methoddesc}[AttributesNS]{getNameByQName}{name}
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Return the \code{(\var{namespace}, \var{localname})} pair for a
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qualified \var{name}.
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\end{methoddesc}
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\begin{methoddesc}[AttributesNS]{getQNameByName}{name}
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Return the qualified name for a \code{(\var{namespace},
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\var{localname})} pair.
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\end{methoddesc}
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\begin{methoddesc}[AttributesNS]{getQNames}{}
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Return the qualified names of all attributes.
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\end{methoddesc}
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