\section{\module{xml.sax.xmlreader} ---
        Interface for XML parsers}

\declaremodule{standard}{xml.sax.xmlreader}
\modulesynopsis{Interface which SAX-compliant XML parsers must implement.}
\sectionauthor{Martin v. L\"owis}{[email protected]}
\moduleauthor{Lars Marius Garshol}{[email protected]}

\versionadded{2.0}


SAX parsers implement the \class{XMLReader} interface. They are
implemented in a Python module, which must provide a function
\function{create_parser()}. This function is invoked by
\function{xml.sax.make_parser()} with no arguments to create a new
parser object.

\begin{classdesc}{XMLReader}{}
 Base class which can be inherited by SAX parsers.
\end{classdesc}

\begin{classdesc}{IncrementalParser}{}
 In some cases, it is desirable not to parse an input source at once,
 but to feed chunks of the document as they get available. Note that
 the reader will normally not read the entire file, but read it in
 chunks as well; still \method{parse()} won't return until the entire
 document is processed. So these interfaces should be used if the
 blocking behaviour of \method{parse()} is not desirable.

 When the parser is instantiated it is ready to begin accepting data
 from the feed method immediately. After parsing has been finished
 with a call to close the reset method must be called to make the
 parser ready to accept new data, either from feed or using the parse
 method.

 Note that these methods must \emph{not} be called during parsing,
 that is, after parse has been called and before it returns.

 By default, the class also implements the parse method of the
 XMLReader interface using the feed, close and reset methods of the
 IncrementalParser interface as a convenience to SAX 2.0 driver
 writers.
\end{classdesc}

\begin{classdesc}{Locator}{}
 Interface for associating a SAX event with a document location. A
 locator object will return valid results only during calls to
 DocumentHandler methods; at any other time, the results are
 unpredictable. If information is not available, methods may return
 \code{None}.
\end{classdesc}

\begin{classdesc}{InputSource}{\optional{systemId}}
 Encapsulation of the information needed by the \class{XMLReader} to
 read entities.

 This class may include information about the public identifier,
 system identifier, byte stream (possibly with character encoding
 information) and/or the character stream of an entity.

 Applications will create objects of this class for use in the
 \method{XMLReader.parse()} method and for returning from
 EntityResolver.resolveEntity.

 An \class{InputSource} belongs to the application, the
 \class{XMLReader} is not allowed to modify \class{InputSource} objects
 passed to it from the application, although it may make copies and
 modify those.
\end{classdesc}

\begin{classdesc}{AttributesImpl}{attrs}
 This is an implementation of the \ulink{\class{Attributes}
 interface}{attributes-objects.html} (see
 section~\ref{attributes-objects}).  This is a dictionary-like
 object which represents the element attributes in a
 \method{startElement()} call. In addition to the most useful
 dictionary operations, it supports a number of other methods as
 described by the interface. Objects of this class should be
 instantiated by readers; \var{attrs} must be a dictionary-like
 object containing a mapping from attribute names to attribute
 values.
\end{classdesc}

\begin{classdesc}{AttributesNSImpl}{attrs, qnames}
 Namespace-aware variant of \class{AttributesImpl}, which will be
 passed to \method{startElementNS()}. It is derived from
 \class{AttributesImpl}, but understands attribute names as
 two-tuples of \var{namespaceURI} and \var{localname}. In addition,
 it provides a number of methods expecting qualified names as they
 appear in the original document.  This class implements the
 \ulink{\class{AttributesNS} interface}{attributes-ns-objects.html}
 (see section~\ref{attributes-ns-objects}).
\end{classdesc}


\subsection{XMLReader Objects \label{xmlreader-objects}}

The \class{XMLReader} interface supports the following methods:

\begin{methoddesc}[XMLReader]{parse}{source}
 Process an input source, producing SAX events. The \var{source}
 object can be a system identifier (a string identifying the
 input source -- typically a file name or an URL), a file-like
 object, or an \class{InputSource} object. When \method{parse()}
 returns, the input is completely processed, and the parser object
 can be discarded or reset. As a limitation, the current implementation
 only accepts byte streams; processing of character streams is for
 further study.
\end{methoddesc}

\begin{methoddesc}[XMLReader]{getContentHandler}{}
 Return the current \class{ContentHandler}.
\end{methoddesc}

\begin{methoddesc}[XMLReader]{setContentHandler}{handler}
 Set the current \class{ContentHandler}.  If no
 \class{ContentHandler} is set, content events will be discarded.
\end{methoddesc}

\begin{methoddesc}[XMLReader]{getDTDHandler}{}
 Return the current \class{DTDHandler}.
\end{methoddesc}

\begin{methoddesc}[XMLReader]{setDTDHandler}{handler}
 Set the current \class{DTDHandler}.  If no \class{DTDHandler} is
 set, DTD events will be discarded.
\end{methoddesc}

\begin{methoddesc}[XMLReader]{getEntityResolver}{}
 Return the current \class{EntityResolver}.
\end{methoddesc}

\begin{methoddesc}[XMLReader]{setEntityResolver}{handler}
 Set the current \class{EntityResolver}.  If no
 \class{EntityResolver} is set, attempts to resolve an external
 entity will result in opening the system identifier for the entity,
 and fail if it is not available.
\end{methoddesc}

\begin{methoddesc}[XMLReader]{getErrorHandler}{}
 Return the current \class{ErrorHandler}.
\end{methoddesc}

\begin{methoddesc}[XMLReader]{setErrorHandler}{handler}
 Set the current error handler.  If no \class{ErrorHandler} is set,
 errors will be raised as exceptions, and warnings will be printed.
\end{methoddesc}

\begin{methoddesc}[XMLReader]{setLocale}{locale}
 Allow an application to set the locale for errors and warnings.

 SAX parsers are not required to provide localization for errors and
 warnings; if they cannot support the requested locale, however, they
 must throw a SAX exception.  Applications may request a locale change
 in the middle of a parse.
\end{methoddesc}

\begin{methoddesc}[XMLReader]{getFeature}{featurename}
 Return the current setting for feature \var{featurename}.  If the
 feature is not recognized, \exception{SAXNotRecognizedException} is
 raised. The well-known featurenames are listed in the module
 \module{xml.sax.handler}.
\end{methoddesc}

\begin{methoddesc}[XMLReader]{setFeature}{featurename, value}
 Set the \var{featurename} to \var{value}. If the feature is not
 recognized, \exception{SAXNotRecognizedException} is raised. If the
 feature or its setting is not supported by the parser,
 \var{SAXNotSupportedException} is raised.
\end{methoddesc}

\begin{methoddesc}[XMLReader]{getProperty}{propertyname}
 Return the current setting for property \var{propertyname}. If the
 property is not recognized, a \exception{SAXNotRecognizedException}
 is raised. The well-known propertynames are listed in the module
 \module{xml.sax.handler}.
\end{methoddesc}

\begin{methoddesc}[XMLReader]{setProperty}{propertyname, value}
 Set the \var{propertyname} to \var{value}. If the property is not
 recognized, \exception{SAXNotRecognizedException} is raised. If the
 property or its setting is not supported by the parser,
 \var{SAXNotSupportedException} is raised.
\end{methoddesc}


\subsection{IncrementalParser Objects
           \label{incremental-parser-objects}}

Instances of \class{IncrementalParser} offer the following additional
methods:

\begin{methoddesc}[IncrementalParser]{feed}{data}
 Process a chunk of \var{data}.
\end{methoddesc}

\begin{methoddesc}[IncrementalParser]{close}{}
 Assume the end of the document. That will check well-formedness
 conditions that can be checked only at the end, invoke handlers, and
 may clean up resources allocated during parsing.
\end{methoddesc}

\begin{methoddesc}[IncrementalParser]{reset}{}
 This method is called after close has been called to reset the
 parser so that it is ready to parse new documents. The results of
 calling parse or feed after close without calling reset are
 undefined.
\end{methoddesc}


\subsection{Locator Objects \label{locator-objects}}

Instances of \class{Locator} provide these methods:

\begin{methoddesc}[Locator]{getColumnNumber}{}
 Return the column number where the current event ends.
\end{methoddesc}

\begin{methoddesc}[Locator]{getLineNumber}{}
 Return the line number where the current event ends.
\end{methoddesc}

\begin{methoddesc}[Locator]{getPublicId}{}
 Return the public identifier for the current event.
\end{methoddesc}

\begin{methoddesc}[Locator]{getSystemId}{}
 Return the system identifier for the current event.
\end{methoddesc}


\subsection{InputSource Objects \label{input-source-objects}}

\begin{methoddesc}[InputSource]{setPublicId}{id}
 Sets the public identifier of this \class{InputSource}.
\end{methoddesc}

\begin{methoddesc}[InputSource]{getPublicId}{}
 Returns the public identifier of this \class{InputSource}.
\end{methoddesc}

\begin{methoddesc}[InputSource]{setSystemId}{id}
 Sets the system identifier of this \class{InputSource}.
\end{methoddesc}

\begin{methoddesc}[InputSource]{getSystemId}{}
 Returns the system identifier of this \class{InputSource}.
\end{methoddesc}

\begin{methoddesc}[InputSource]{setEncoding}{encoding}
 Sets the character encoding of this \class{InputSource}.

 The encoding must be a string acceptable for an XML encoding
 declaration (see section 4.3.3 of the XML recommendation).

 The encoding attribute of the \class{InputSource} is ignored if the
 \class{InputSource} also contains a character stream.
\end{methoddesc}

\begin{methoddesc}[InputSource]{getEncoding}{}
 Get the character encoding of this InputSource.
\end{methoddesc}

\begin{methoddesc}[InputSource]{setByteStream}{bytefile}
 Set the byte stream (a Python file-like object which does not
 perform byte-to-character conversion) for this input source.

 The SAX parser will ignore this if there is also a character stream
 specified, but it will use a byte stream in preference to opening a
 URI connection itself.

 If the application knows the character encoding of the byte stream,
 it should set it with the setEncoding method.
\end{methoddesc}

\begin{methoddesc}[InputSource]{getByteStream}{}
 Get the byte stream for this input source.

 The getEncoding method will return the character encoding for this
 byte stream, or None if unknown.
\end{methoddesc}

\begin{methoddesc}[InputSource]{setCharacterStream}{charfile}
 Set the character stream for this input source. (The stream must be
 a Python 1.6 Unicode-wrapped file-like that performs conversion to
 Unicode strings.)

 If there is a character stream specified, the SAX parser will ignore
 any byte stream and will not attempt to open a URI connection to the
 system identifier.
\end{methoddesc}

\begin{methoddesc}[InputSource]{getCharacterStream}{}
 Get the character stream for this input source.
\end{methoddesc}


\subsection{The \class{Attributes} Interface \label{attributes-objects}}

\class{Attributes} objects implement a portion of the mapping
protocol, including the methods \method{copy()}, \method{get()},
\method{has_key()}, \method{items()}, \method{keys()}, and
\method{values()}.  The following methods are also provided:

\begin{methoddesc}[Attributes]{getLength}{}
 Return the number of attributes.
\end{methoddesc}

\begin{methoddesc}[Attributes]{getNames}{}
 Return the names of the attributes.
\end{methoddesc}

\begin{methoddesc}[Attributes]{getType}{name}
 Returns the type of the attribute \var{name}, which is normally
 \code{'CDATA'}.
\end{methoddesc}

\begin{methoddesc}[Attributes]{getValue}{name}
 Return the value of attribute \var{name}.
\end{methoddesc}

% getValueByQName, getNameByQName, getQNameByName, getQNames available
% here already, but documented only for derived class.


\subsection{The \class{AttributesNS} Interface \label{attributes-ns-objects}}

This interface is a subtype of the \ulink{\class{Attributes}
interface}{attributes-objects.html} (see
section~\ref{attributes-objects}).  All methods supported by that
interface are also available on \class{AttributesNS} objects.

The following methods are also available:

\begin{methoddesc}[AttributesNS]{getValueByQName}{name}
 Return the value for a qualified name.
\end{methoddesc}

\begin{methoddesc}[AttributesNS]{getNameByQName}{name}
 Return the \code{(\var{namespace}, \var{localname})} pair for a
 qualified \var{name}.
\end{methoddesc}

\begin{methoddesc}[AttributesNS]{getQNameByName}{name}
 Return the qualified name for a \code{(\var{namespace},
 \var{localname})} pair.
\end{methoddesc}

\begin{methoddesc}[AttributesNS]{getQNames}{}
 Return the qualified names of all attributes.
\end{methoddesc}

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