20.12. "xml.sax.xmlreader" — Interface for XML parsers
******************************************************

**Source code:** Lib/xml/sax/xmlreader.py

======================================================================

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

class xml.sax.xmlreader.XMLReader

   Base class which can be inherited by SAX parsers.

class xml.sax.xmlreader.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 "parse()" won’t return until the
   entire document is processed. So these interfaces should be used if
   the blocking behaviour of "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 *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.

class xml.sax.xmlreader.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
   "None".

class xml.sax.xmlreader.InputSource(system_id=None)

   Encapsulation of the information needed by the "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
   "XMLReader.parse()" method and for returning from
   EntityResolver.resolveEntity.

   An "InputSource" belongs to the application, the "XMLReader" is not
   allowed to modify "InputSource" objects passed to it from the
   application, although it may make copies and modify those.

class xml.sax.xmlreader.AttributesImpl(attrs)

   This is an implementation of the "Attributes" interface (see
   section The Attributes Interface).  This is a dictionary-like
   object which represents the element attributes in a
   "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; *attrs* must be a dictionary-like object containing a
   mapping from attribute names to attribute values.

class xml.sax.xmlreader.AttributesNSImpl(attrs, qnames)

   Namespace-aware variant of "AttributesImpl", which will be passed
   to "startElementNS()". It is derived from "AttributesImpl", but
   understands attribute names as two-tuples of *namespaceURI* and
   *localname*. In addition, it provides a number of methods expecting
   qualified names as they appear in the original document.  This
   class implements the "AttributesNS" interface (see section The
   AttributesNS Interface).


20.12.1. XMLReader Objects
==========================

The "XMLReader" interface supports the following methods:

XMLReader.parse(source)

   Process an input source, producing SAX events. The *source* object
   can be a system identifier (a string identifying the input source –
   typically a file name or a URL), a file-like object, or an
   "InputSource" object. When "parse()" returns, the input is
   completely processed, and the parser object can be discarded or
   reset.

   Changed in version 3.5: Added support of character streams.

XMLReader.getContentHandler()

   Return the current "ContentHandler".

XMLReader.setContentHandler(handler)

   Set the current "ContentHandler".  If no "ContentHandler" is set,
   content events will be discarded.

XMLReader.getDTDHandler()

   Return the current "DTDHandler".

XMLReader.setDTDHandler(handler)

   Set the current "DTDHandler".  If no "DTDHandler" is set, DTD
   events will be discarded.

XMLReader.getEntityResolver()

   Return the current "EntityResolver".

XMLReader.setEntityResolver(handler)

   Set the current "EntityResolver".  If no "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.

XMLReader.getErrorHandler()

   Return the current "ErrorHandler".

XMLReader.setErrorHandler(handler)

   Set the current error handler.  If no "ErrorHandler" is set, errors
   will be raised as exceptions, and warnings will be printed.

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 raise a SAX exception.  Applications may request a locale
   change in the middle of a parse.

XMLReader.getFeature(featurename)

   Return the current setting for feature *featurename*.  If the
   feature is not recognized, "SAXNotRecognizedException" is raised.
   The well-known featurenames are listed in the module
   "xml.sax.handler".

XMLReader.setFeature(featurename, value)

   Set the *featurename* to *value*. If the feature is not recognized,
   "SAXNotRecognizedException" is raised. If the feature or its
   setting is not supported by the parser, *SAXNotSupportedException*
   is raised.

XMLReader.getProperty(propertyname)

   Return the current setting for property *propertyname*. If the
   property is not recognized, a "SAXNotRecognizedException" is
   raised. The well-known propertynames are listed in the module
   "xml.sax.handler".

XMLReader.setProperty(propertyname, value)

   Set the *propertyname* to *value*. If the property is not
   recognized, "SAXNotRecognizedException" is raised. If the property
   or its setting is not supported by the parser,
   *SAXNotSupportedException* is raised.


20.12.2. IncrementalParser Objects
==================================

Instances of "IncrementalParser" offer the following additional
methods:

IncrementalParser.feed(data)

   Process a chunk of *data*.

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.

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.


20.12.3. Locator Objects
========================

Instances of "Locator" provide these methods:

Locator.getColumnNumber()

   Return the column number where the current event begins.

Locator.getLineNumber()

   Return the line number where the current event begins.

Locator.getPublicId()

   Return the public identifier for the current event.

Locator.getSystemId()

   Return the system identifier for the current event.


20.12.4. InputSource Objects
============================

InputSource.setPublicId(id)

   Sets the public identifier of this "InputSource".

InputSource.getPublicId()

   Returns the public identifier of this "InputSource".

InputSource.setSystemId(id)

   Sets the system identifier of this "InputSource".

InputSource.getSystemId()

   Returns the system identifier of this "InputSource".

InputSource.setEncoding(encoding)

   Sets the character encoding of this "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 "InputSource" is ignored if the
   "InputSource" also contains a character stream.

InputSource.getEncoding()

   Get the character encoding of this InputSource.

InputSource.setByteStream(bytefile)

   Set the byte stream (a *binary file*) 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.

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.

InputSource.setCharacterStream(charfile)

   Set the character stream (a *text file*) for this input source.

   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.

InputSource.getCharacterStream()

   Get the character stream for this input source.


20.12.5. The "Attributes" Interface
===================================

"Attributes" objects implement a portion of the *mapping protocol*,
including the methods "copy()", "get()", "__contains__()", "items()",
"keys()", and "values()".  The following methods are also provided:

Attributes.getLength()

   Return the number of attributes.

Attributes.getNames()

   Return the names of the attributes.

Attributes.getType(name)

   Returns the type of the attribute *name*, which is normally
   "'CDATA'".

Attributes.getValue(name)

   Return the value of attribute *name*.


20.12.6. The "AttributesNS" Interface
=====================================

This interface is a subtype of the "Attributes" interface (see section
The Attributes Interface).  All methods supported by that interface
are also available on "AttributesNS" objects.

The following methods are also available:

AttributesNS.getValueByQName(name)

   Return the value for a qualified name.

AttributesNS.getNameByQName(name)

   Return the "(namespace, localname)" pair for a qualified *name*.

AttributesNS.getQNameByName(name)

   Return the qualified name for a "(namespace, localname)" pair.

AttributesNS.getQNames()

   Return the qualified names of all attributes.
