xml.sax.handler — lxml documentation

# Source code for xml.sax.handler

    """
    This module contains the core classes of version 2.0 of SAX for Python.
    This file provides only default classes with absolutely minimum
    functionality, from which drivers and applications can be subclassed.

    Many of these classes are empty and are included only as documentation
    of the interfaces.

    $Id$
    """

    version = '2.0beta'

    #============================================================================
    #
    # HANDLER INTERFACES
    #
    #============================================================================

    # ===== ERRORHANDLER =====

    class ErrorHandler:
        """Basic interface for SAX error handlers.

        If you create an object that implements this interface, then
        register the object with your XMLReader, the parser will call the
        methods in your object to report all warnings and errors. There
        are three levels of errors available: warnings, (possibly)
        recoverable errors, and unrecoverable errors. All methods take a
        SAXParseException as the only parameter."""

        def error(self, exception):
            "Handle a recoverable error."
            raise exception

        def fatalError(self, exception):
            "Handle a non-recoverable error."
            raise exception

        def warning(self, exception):
            "Handle a warning."
            print(exception)

    # ===== CONTENTHANDLER =====

    class ContentHandler:
        """Interface for receiving logical document content events.

        This is the main callback interface in SAX, and the one most
        important to applications. The order of events in this interface
        mirrors the order of the information in the document."""

        def __init__(self):
            self._locator = None

        def setDocumentLocator(self, 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."""
            self._locator = locator

        def startDocument(self):
            """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)."""

        def endDocument(self):
            """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."""

        def startPrefixMapping(self, 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."""

        def endPrefixMapping(self, 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."""

        def startElement(self, 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."""

        def endElement(self, 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."""

        def startElementNS(self, 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 Attributes class containing the
            attributes of the element.

            The uri part of the name tuple is None for elements which have
            no namespace."""

        def endElementNS(self, 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."""

        def characters(self, 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."""

        def ignorableWhitespace(self, whitespace):
            """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."""

        def processingInstruction(self, 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."""

        def skippedEntity(self, 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."""

    # ===== DTDHandler =====

    class DTDHandler:
        """Handle DTD events.

        This interface specifies only those DTD events required for basic
        parsing (unparsed entities and attributes)."""

        def notationDecl(self, name, publicId, systemId):
            "Handle a notation declaration event."

        def unparsedEntityDecl(self, name, publicId, systemId, ndata):
            "Handle an unparsed entity declaration event."

    # ===== ENTITYRESOLVER =====

    class EntityResolver:
        """Basic interface for resolving entities. If you create an object
        implementing this interface, then register the object with your
        Parser, the parser will call the method in your object to
        resolve all external entities. Note that DefaultHandler implements
        this interface with the default behaviour."""

        def resolveEntity(self, publicId, systemId):
            """Resolve the system identifier of an entity and return either
            the system identifier to read from as a string, or an InputSource
            to read from."""
            return systemId

    #============================================================================
    #
    # CORE FEATURES
    #
    #============================================================================

    feature_namespaces = "http://xml.org/sax/features/namespaces"
    # true: Perform Namespace processing (default).
    # false: Optionally do not perform Namespace processing
    #        (implies namespace-prefixes).
    # access: (parsing) read-only; (not parsing) read/write

    feature_namespace_prefixes = "http://xml.org/sax/features/namespace-prefixes"
    # true: Report the original prefixed names and attributes used for Namespace
    #       declarations.
    # false: Do not report attributes used for Namespace declarations, and
    #        optionally do not report original prefixed names (default).
    # access: (parsing) read-only; (not parsing) read/write

    feature_string_interning = "http://xml.org/sax/features/string-interning"
    # true: All element names, prefixes, attribute names, Namespace URIs, and
    #       local names are interned using the built-in intern function.
    # false: Names are not necessarily interned, although they may be (default).
    # access: (parsing) read-only; (not parsing) read/write

    feature_validation = "http://xml.org/sax/features/validation"
    # true: Report all validation errors (implies external-general-entities and
    #       external-parameter-entities).
    # false: Do not report validation errors.
    # access: (parsing) read-only; (not parsing) read/write

    feature_external_ges = "http://xml.org/sax/features/external-general-entities"
    # true: Include all external general (text) entities.
    # false: Do not include external general entities.
    # access: (parsing) read-only; (not parsing) read/write

    feature_external_pes = "http://xml.org/sax/features/external-parameter-entities"
    # true: Include all external parameter entities, including the external
    #       DTD subset.
    # false: Do not include any external parameter entities, even the external
    #        DTD subset.
    # access: (parsing) read-only; (not parsing) read/write

    all_features = [feature_namespaces,
                    feature_namespace_prefixes,
                    feature_string_interning,
                    feature_validation,
                    feature_external_ges,
                    feature_external_pes]

    #============================================================================
    #
    # CORE PROPERTIES
    #
    #============================================================================

    property_lexical_handler = "http://xml.org/sax/properties/lexical-handler"
    # data type: xml.sax.sax2lib.LexicalHandler
    # description: An optional extension handler for lexical events like comments.
    # access: read/write

    property_declaration_handler = "http://xml.org/sax/properties/declaration-handler"
    # data type: xml.sax.sax2lib.DeclHandler
    # description: An optional extension handler for DTD-related events other
    #              than notations and unparsed entities.
    # access: read/write

    property_dom_node = "http://xml.org/sax/properties/dom-node"
    # data type: org.w3c.dom.Node
    # description: When parsing, the current DOM node being visited if this is
    #              a DOM iterator; when not parsing, the root DOM node for
    #              iteration.
    # access: (parsing) read-only; (not parsing) read/write

    property_xml_string = "http://xml.org/sax/properties/xml-string"
    # data type: String
    # description: The literal string of characters that was the source for
    #              the current event.
    # access: read-only

    property_encoding = "http://www.python.org/sax/properties/encoding"
    # data type: String
    # description: The name of the encoding to assume for input data.
    # access: write: set the encoding, e.g. established by a higher-level
    #                protocol. May change during parsing (e.g. after
    #                processing a META tag)
    #         read:  return the current encoding (possibly established through
    #                auto-detection.
    # initial value: UTF-8
    #

    property_interning_dict = "http://www.python.org/sax/properties/interning-dict"
    # data type: Dictionary
    # description: The dictionary used to intern common strings in the document
    # access: write: Request that the parser uses a specific dictionary, to
    #                allow interning across different documents
    #         read:  return the current interning dictionary, or None
    #

    all_properties = [property_lexical_handler,
                      property_dom_node,
                      property_declaration_handler,
                      property_xml_string,
                      property_encoding,
                      property_interning_dict]

    class LexicalHandler:
        """Optional SAX2 handler for lexical events.

        This handler is used to obtain lexical information about an XML
        document, that is, information about how the document was encoded
        (as opposed to what it contains, which is reported to the
        ContentHandler), such as comments and CDATA marked section
        boundaries.

        To set the LexicalHandler of an XMLReader, use the setProperty
        method with the property identifier
        'http://xml.org/sax/properties/lexical-handler'."""

        def comment(self, content):
            """Reports a comment anywhere in the document (including the
            DTD and outside the document element).

            content is a string that holds the contents of the comment."""

        def startDTD(self, name, public_id, system_id):
            """Report the start of the DTD declarations, if the document
            has an associated DTD.

            A startEntity event will be reported before declaration events
            from the external DTD subset are reported, and this can be
            used to infer from which subset DTD declarations derive.

            name is the name of the document element type, public_id the
            public identifier of the DTD (or None if none were supplied)
            and system_id the system identfier of the external subset (or
            None if none were supplied)."""

        def endDTD(self):
            """Signals the end of DTD declarations."""

        def startCDATA(self):
            """Reports the beginning of a CDATA marked section.

            The contents of the CDATA marked section will be reported
            through the characters event."""

        def endCDATA(self):
            """Reports the end of a CDATA marked section."""