xml.sax.xmlreader —- Interface for XML parsers

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

SAX parsers implement the XMLReader interface. They are implemented ina Python module, which must provide a function create_parser(). Thisfunction is invoked by xml.sax.make_parser() with no arguments to createa 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 feedchunks of the document as they get available. Note that the reader will normallynot 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 shouldbe used if the blocking behaviour of parse() is not desirable.

When the parser is instantiated it is ready to begin accepting data from thefeed method immediately. After parsing has been finished with a call to closethe 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, afterparse has been called and before it returns.

By default, the class also implements the parse method of the XMLReaderinterface using the feed, close and reset methods of the IncrementalParserinterface 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 objectwill return valid results only during calls to DocumentHandler methods; at anyother 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 readentities.

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

Applications will create objects of this class for use in theXMLReader.parse() method and for returning fromEntityResolver.resolveEntity.

An InputSource belongs to the application, the XMLReader isnot allowed to modify InputSource objects passed to it from theapplication, although it may make copies and modify those.

• class xml.sax.xmlreader.AttributesImpl(attrs)

• This is an implementation of the Attributes interface (see sectionThe Attributes Interface). This is a dictionary-like object whichrepresents the element attributes in a startElement() call. In additionto the most useful dictionary operations, it supports a number of othermethods as described by the interface. Objects of this class should beinstantiated by readers; attrs must be a dictionary-like object containinga mapping from attribute names to attribute values.

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

• Namespace-aware variant of AttributesImpl, which will be passed tostartElementNS(). It is derived from AttributesImpl, butunderstands attribute names as two-tuples of namespaceURI andlocalname. In addition, it provides a number of methods expecting qualifiednames as they appear in the original document. This class implements theAttributesNS interface (see section The AttributesNS Interface).

XMLReader 对象

The XMLReader interface supports the following methods:

• XMLReader.parse(source)
• Process an input source, producing SAX events. The source object can be asystem identifier (a string identifying the input source — typically a filename or a URL), a pathlib.Path or path-likeobject, or an InputSource object. Whenparse() returns, the input is completely processed, and the parser objectcan be discarded or reset.

在 3.5 版更改: Added support of character streams.

在 3.8 版更改: Added support of path-like objects.

• XMLReader.getContentHandler()

• Return the current ContentHandler.

• XMLReader.setContentHandler(handler)

• Set the current ContentHandler. If noContentHandler is set, content events will bediscarded.

• XMLReader.getDTDHandler()

• Return the current DTDHandler.

• XMLReader.setDTDHandler(handler)

• Set the current DTDHandler. If noDTDHandler is set, DTDevents will be discarded.

• XMLReader.getEntityResolver()

• Return the current EntityResolver.

• XMLReader.setEntityResolver(handler)

• Set the current EntityResolver. If noEntityResolver is set,attempts to resolve an external entity will result in opening the systemidentifier 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 ErrorHandleris 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; ifthey cannot support the requested locale, however, they must raise a SAXexception. 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 notrecognized, SAXNotRecognizedException is raised. The well-knownfeaturenames 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 notsupported by the parser, SAXNotSupportedException is raised.

• XMLReader.getProperty(propertyname)

• Return the current setting for property propertyname. If the property is notrecognized, a SAXNotRecognizedException is raised. The well-knownpropertynames 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 isnot supported by the parser, SAXNotSupportedException is raised.

IncrementalParser 对象

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 thatcan be checked only at the end, invoke handlers, and may clean up resourcesallocated during parsing.

• IncrementalParser.reset()

• This method is called after close has been called to reset the parser so that itis ready to parse new documents. The results of calling parse or feed afterclose without calling reset are undefined.

Locator 对象

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.

InputSource 对象

• 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 (seesection 4.3.3 of the XML recommendation).

The encoding attribute of the InputSource is ignored if theInputSource 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 shouldset 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 bytestream and will not attempt to open a URI connection to the system identifier.

• InputSource.getCharacterStream()
• Get the character stream for this input source.

The Attributes Interface

Attributes objects implement a portion of the mapping protocol, including the methods copy(),get(), contains(),items(), keys(),and values(). The following methodsare 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.

The AttributesNS Interface

This interface is a subtype of the Attributes interface (see sectionThe Attributes Interface). All methods supported by that interface are alsoavailable 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.