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(python2.1-lib.info)ContentHandler Objects
ContentHandler Objects
----------------------
Users are expected to subclass `ContentHandler' to support their
application. The following methods are called by the parser on the
appropriate events in the input document:
`setDocumentLocator(locator)'
Called by the parser to give the application a locator for locating
the origin of document events.
SAX parsers are strongly encouraged (though not absolutely
required) to supply a locator: if it does so, it must supply the
locator to the application by invoking this method before invoking
any of the other methods in the DocumentHandler interface.
The locator allows the application to determine the end position of
any document-related event, even if the parser is not reporting an
error. Typically, the application will use this information for
reporting its own errors (such as character content that does not
match an application's business rules). The information returned by
the locator is probably not sufficient for use with a search
engine.
Note that the locator will return correct information only during
the invocation of the events in this interface. The application
should not attempt to use it at any other time.
`startDocument()'
Receive notification of the beginning of a document.
The SAX parser will invoke this method only once, before any other
methods in this interface or in DTDHandler (except for
`setDocumentLocator()').
`endDocument()'
Receive notification of the end of a document.
The SAX parser will invoke this method only once, and it will be
the last method invoked during the parse. The parser shall not
invoke this method until it has either abandoned parsing (because
of an unrecoverable error) or reached the end of input.
`startPrefixMapping(prefix, uri)'
Begin the scope of a prefix-URI Namespace mapping.
The information from this event is not necessary for normal
Namespace processing: the SAX XML reader will automatically replace
prefixes for element and attribute names when the
`http://xml.org/sax/features/namespaces' feature is true (the
default).
There are cases, however, when applications need to use prefixes in
character data or in attribute values, where they cannot safely be
expanded automatically; the start/endPrefixMapping event supplies
the information to the application to expand prefixes in those
contexts itself, if necessary.
Note that start/endPrefixMapping events are not guaranteed to be
properly nested relative to each-other: all `startPrefixMapping()'
events will occur before the corresponding startElement event, and
all `endPrefixMapping()' events will occur after the corresponding
`endElement()' event, but their order is not guaranteed.
`endPrefixMapping(prefix)'
End the scope of a prefix-URI mapping.
See `startPrefixMapping()' for details. This event will always
occur after the corresponding endElement event, but the order of
endPrefixMapping events is not otherwise guaranteed.
`startElement(name, attrs)'
Signals the start of an element in non-namespace mode.
The NAME parameter contains the raw XML 1.0 name of the element
type as a string and the ATTRS parameter holds an instance of the
`Attributes' class containing the attributes of the element.
`endElement(name)'
Signals the end of an element in non-namespace mode.
The NAME parameter contains the name of the element type, just as
with the startElement event.
`startElementNS(name, qname, attrs)'
Signals the start of an element in namespace mode.
The NAME parameter contains the name of the element type as a
(uri, localname) tuple, the QNAME parameter the raw XML 1.0 name
used in the source document, and the ATTRS parameter holds an
instance of the `AttributesNS' class containing the attributes of
the element.
Parsers may set the QNAME parameter to `None', unless the
`http://xml.org/sax/features/namespace-prefixes' feature is
activated.
`endElementNS(name, qname)'
Signals the end of an element in namespace mode.
The NAME parameter contains the name of the element type, just as
with the startElementNS event, likewise the QNAME parameter.
`characters(content)'
Receive notification of character data.
The Parser will call this method to report each chunk of character
data. SAX parsers may return all contiguous character data in a
single chunk, or they may split it into several chunks; however,
all of the characters in any single event must come from the same
external entity so that the Locator provides useful information.
CONTENT may be a Unicode string or a byte string; the `expat'
reader module produces always Unicode strings.
*Note:* The earlier SAX 1 interface provided by the Python XML
Special Interest Group used a more Java-like interface for this
method. Since most parsers used from Python did not take advantage
of the older interface, the simpler signature was chosen to replace
it. To convert old code to the new interface, use CONTENT instead
of slicing content with the old OFFSET and LENGTH parameters.
`ignorableWhitespace()'
Receive notification of ignorable whitespace in element content.
Validating Parsers must use this method to report each chunk of
ignorable whitespace (see the W3C XML 1.0 recommendation, section
2.10): non-validating parsers may also use this method if they are
capable of parsing and using content models.
SAX parsers may return all contiguous whitespace in a single
chunk, or they may split it into several chunks; however, all of
the characters in any single event must come from the same
external entity, so that the Locator provides useful information.
`processingInstruction(target, data)'
Receive notification of a processing instruction.
The Parser will invoke this method once for each processing
instruction found: note that processing instructions may occur
before or after the main document element.
A SAX parser should never report an XML declaration (XML 1.0,
section 2.8) or a text declaration (XML 1.0, section 4.3.1) using
this method.
`skippedEntity(name)'
Receive notification of a skipped entity.
The Parser will invoke this method once for each entity skipped.
Non-validating processors may skip entities if they have not seen
the declarations (because, for example, the entity was declared in
an external DTD subset). All processors may skip external
entities, depending on the values of the
`http://xml.org/sax/features/external-general-entities' and the
`http://xml.org/sax/features/external-parameter-entities'
properties.
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