20.9. xml.sax
— Support for SAX2 parsers¶
Source code: Lib/xml/sax/__init__.py
The xml.sax
package provides a number of modules which implement the
Simple API for XML (SAX) interface for Python. The package itself provides the
SAX exceptions and the convenience functions which will be most used by users of
the SAX API.
警告
The xml.sax
module is not secure against maliciously
constructed data. If you need to parse untrusted or unauthenticated data see
XML vulnerabilities.
The convenience functions are:
-
xml.sax.
make_parser
(parser_list=[])¶ Create and return a SAX
XMLReader
object. The first parser found will be used. If parser_list is provided, it must be a sequence of strings which name modules that have a function namedcreate_parser()
. Modules listed in parser_list will be used before modules in the default list of parsers.
-
xml.sax.
parse
(filename_or_stream, handler, error_handler=handler.ErrorHandler())¶ Create a SAX parser and use it to parse a document. The document, passed in as filename_or_stream, can be a filename or a file object. The handler parameter needs to be a SAX
ContentHandler
instance. If error_handler is given, it must be a SAXErrorHandler
instance; if omitted,SAXParseException
will be raised on all errors. There is no return value; all work must be done by the handler passed in.
-
xml.sax.
parseString
(string, handler, error_handler=handler.ErrorHandler())¶ Similar to
parse()
, but parses from a buffer string received as a parameter. string must be astr
instance or a bytes-like object.在 3.5 版更改: Added support of
str
instances.
A typical SAX application uses three kinds of objects: readers, handlers and input sources. “Reader” in this context is another term for parser, i.e. some piece of code that reads the bytes or characters from the input source, and produces a sequence of events. The events then get distributed to the handler objects, i.e. the reader invokes a method on the handler. A SAX application must therefore obtain a reader object, create or open the input sources, create the handlers, and connect these objects all together. As the final step of preparation, the reader is called to parse the input. During parsing, methods on the handler objects are called based on structural and syntactic events from the input data.
For these objects, only the interfaces are relevant; they are normally not
instantiated by the application itself. Since Python does not have an explicit
notion of interface, they are formally introduced as classes, but applications
may use implementations which do not inherit from the provided classes. The
InputSource
, Locator
,
Attributes
, AttributesNS
,
and XMLReader
interfaces are defined in the
module xml.sax.xmlreader
. The handler interfaces are defined in
xml.sax.handler
. For convenience,
InputSource
(which is often
instantiated directly) and the handler classes are also available from
xml.sax
. These interfaces are described below.
In addition to these classes, xml.sax
provides the following exception
classes.
-
exception
xml.sax.
SAXException
(msg, exception=None)¶ Encapsulate an XML error or warning. This class can contain basic error or warning information from either the XML parser or the application: it can be subclassed to provide additional functionality or to add localization. Note that although the handlers defined in the
ErrorHandler
interface receive instances of this exception, it is not required to actually raise the exception — it is also useful as a container for information.When instantiated, msg should be a human-readable description of the error. The optional exception parameter, if given, should be
None
or an exception that was caught by the parsing code and is being passed along as information.This is the base class for the other SAX exception classes.
-
exception
xml.sax.
SAXParseException
(msg, exception, locator)¶ Subclass of
SAXException
raised on parse errors. Instances of this class are passed to the methods of the SAXErrorHandler
interface to provide information about the parse error. This class supports the SAXLocator
interface as well as theSAXException
interface.
-
exception
xml.sax.
SAXNotRecognizedException
(msg, exception=None)¶ Subclass of
SAXException
raised when a SAXXMLReader
is confronted with an unrecognized feature or property. SAX applications and extensions may use this class for similar purposes.
-
exception
xml.sax.
SAXNotSupportedException
(msg, exception=None)¶ Subclass of
SAXException
raised when a SAXXMLReader
is asked to enable a feature that is not supported, or to set a property to a value that the implementation does not support. SAX applications and extensions may use this class for similar purposes.
参见
- SAX: The Simple API for XML
- This site is the focal point for the definition of the SAX API. It provides a Java implementation and online documentation. Links to implementations and historical information are also available.
- Module
xml.sax.handler
- Definitions of the interfaces for application-provided objects.
- Module
xml.sax.saxutils
- Convenience functions for use in SAX applications.
- Module
xml.sax.xmlreader
- Definitions of the interfaces for parser-provided objects.
20.9.1. SAXException Objects¶
The SAXException
exception class supports the following methods:
-
SAXException.
getMessage
()¶ Return a human-readable message describing the error condition.
-
SAXException.
getException
()¶ Return an encapsulated exception object, or
None
.