The SAX API defines four kinds of handlers: content handlers, DTD handlers,error handlers, and entity resolvers. Applications normally only need toimplement those interfaces whose events they are interested in; they canimplement the interfaces in a single object or in multiple objects. Handlerimplementations should inherit from the base classes provided in the modulexml.sax.handler, so that all methods get default implementations.
This is the main callback interface in SAX, and the one most important toapplications. The order of events in this interface mirrors the order of theinformation in the document.
Handle DTD events.
This interface specifies only those DTD events required for basic parsing(unparsed entities and attributes).
Basic interface for resolving entities. If you create an object implementingthis interface, then register the object with your Parser, the parser will callthe method in your object to resolve all external entities.
Interface used by the parser to present error and warning messages to theapplication. The methods of this object control whether errors are immediatelyconverted to exceptions or are handled in some other way.
In addition to these classes,xml.sax.handler provides symbolic constantsfor the feature and property names.
List of all features.
List of all known property names.
Users are expected to subclassContentHandler to support theirapplication. The following methods are called by the parser on the appropriateevents in the input document:
Called by the parser to give the application a locator for locating the originof document events.
SAX parsers are strongly encouraged (though not absolutely required) to supply alocator: if it does so, it must supply the locator to the application byinvoking this method before invoking any of the other methods in theDocumentHandler interface.
The locator allows the application to determine the end position of anydocument-related event, even if the parser is not reporting an error. Typically,the application will use this information for reporting its own errors (such ascharacter content that does not match an application’s business rules). Theinformation returned by the locator is probably not sufficient for use with asearch engine.
Note that the locator will return correct information only during the invocationof the events in this interface. The application should not attempt to use it atany other time.
Receive notification of the beginning of a document.
The SAX parser will invoke this method only once, before any other methods inthis interface or in DTDHandler (except forsetDocumentLocator()).
Receive notification of the end of a document.
The SAX parser will invoke this method only once, and it will be the last methodinvoked during the parse. The parser shall not invoke this method until it haseither abandoned parsing (because of an unrecoverable error) or reached the endof input.
Begin the scope of a prefix-URI Namespace mapping.
The information from this event is not necessary for normal Namespaceprocessing: the SAX XML reader will automatically replace prefixes for elementand attribute names when thefeature_namespaces feature is enabled (thedefault).
There are cases, however, when applications need to use prefixes in characterdata or in attribute values, where they cannot safely be expanded automatically;thestartPrefixMapping() andendPrefixMapping() events supply theinformation to the application to expand prefixes in those contexts itself, ifnecessary.
Note thatstartPrefixMapping() andendPrefixMapping() events are notguaranteed to be properly nested relative to each-other: allstartPrefixMapping() events will occur before the correspondingstartElement() event, and allendPrefixMapping() events will occurafter the correspondingendElement() event, but their order is notguaranteed.
End the scope of a prefix-URI mapping.
SeestartPrefixMapping() for details. This event will always occur afterthe correspondingendElement() event, but the order ofendPrefixMapping() events is not otherwise guaranteed.
Signals the start of an element in non-namespace mode.
Thename parameter contains the raw XML 1.0 name of the element type as astring and theattrs parameter holds an object of theAttributesinterface (seeThe Attributes Interface) containing the attributes ofthe element. The object passed asattrs may be re-used by the parser; holdingon to a reference to it is not a reliable way to keep a copy of the attributes.To keep a copy of the attributes, use thecopy() method of theattrsobject.
Signals the end of an element in non-namespace mode.
Thename parameter contains the name of the element type, just as with thestartElement() event.
Signals the start of an element in namespace mode.
Thename parameter contains the name of the element type as a(uri,localname) tuple, theqname parameter contains the raw XML 1.0 name used inthe source document, and theattrs parameter holds an instance of theAttributesNS interface (seeThe AttributesNS Interface)containing the attributes of the element. If no namespace is associated withthe element, theuri component ofname will beNone. The object passedasattrs may be re-used by the parser; holding on to a reference to it is nota reliable way to keep a copy of the attributes. To keep a copy of theattributes, use thecopy() method of theattrs object.
Parsers may set theqname parameter toNone, unless thefeature_namespace_prefixes feature is activated.
Signals the end of an element in namespace mode.
Thename parameter contains the name of the element type, just as with thestartElementNS() method, likewise theqname parameter.
Receive notification of character data.
The Parser will call this method to report each chunk of character data. SAXparsers may return all contiguous character data in a single chunk, or they maysplit it into several chunks; however, all of the characters in any single eventmust come from the same external entity so that the Locator provides usefulinformation.
content may be a string or bytes instance; theexpat reader modulealways produces strings.
Note
The earlier SAX 1 interface provided by the Python XML Special Interest Groupused a more Java-like interface for this method. Since most parsers used fromPython did not take advantage of the older interface, the simpler signature waschosen to replace it. To convert old code to the new interface, usecontentinstead of slicing content with the oldoffset andlength parameters.
Receive notification of ignorable whitespace in element content.
Validating Parsers must use this method to report each chunk of ignorablewhitespace (see the W3C XML 1.0 recommendation, section 2.10): non-validatingparsers may also use this method if they are capable of parsing and usingcontent models.
SAX parsers may return all contiguous whitespace in a single chunk, or they maysplit it into several chunks; however, all of the characters in any single eventmust come from the same external entity, so that the Locator provides usefulinformation.
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 documentelement.
A SAX parser should never report an XML declaration (XML 1.0, section 2.8) or atext declaration (XML 1.0, section 4.3.1) using this method.
Receive notification of a skipped entity.
The Parser will invoke this method once for each entity skipped. Non-validatingprocessors may skip entities if they have not seen the declarations (because,for example, the entity was declared in an external DTD subset). All processorsmay skip external entities, depending on the values of thefeature_external_ges and thefeature_external_pes properties.
DTDHandler instances provide the following methods:
Handle a notation declaration event.
Handle an unparsed entity declaration event.
Resolve the system identifier of an entity and return either the systemidentifier to read from as a string, or an InputSource to read from. The defaultimplementation returnssystemId.
Objects with this interface are used to receive error and warning informationfrom theXMLReader. If you create an object thatimplements this interface, then register the object with yourXMLReader, the parserwill call the methods in your object to report all warnings and errors. Thereare three levels of errors available: warnings, (possibly) recoverable errors,and unrecoverable errors. All methods take aSAXParseException as theonly parameter. Errors and warnings may be converted to an exception by raisingthe passed-in exception object.
Called when the parser encounters a recoverable error. If this method does notraise an exception, parsing may continue, but further document informationshould not be expected by the application. Allowing the parser to continue mayallow additional errors to be discovered in the input document.
Called when the parser encounters an error it cannot recover from; parsing isexpected to terminate when this method returns.
Called when the parser presents minor warning information to the application.Parsing is expected to continue when this method returns, and documentinformation will continue to be passed to the application. Raising an exceptionin this method will cause parsing to end.
20.9.xml.sax — Support for SAX2 parsers
20.11.xml.sax.saxutils — SAX Utilities
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