ref: 5513dae7d9eee46f7e1843c8eeeaf9066d0ec632
dir: /sys/src/cmd/python/Doc/lib/xmlsaxreader.tex/
\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}{martin@v.loewis.de}
\moduleauthor{Lars Marius Garshol}{larsga@garshol.priv.no}
\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}