Professional IronPython

LISTINg 13-4: 
 Parsing an XML document using SAX
# Import the required module.
import xml.sax
# Create a handler based on the default ContentHandler class.
class MessageHandler(xml.sax.ContentHandler):
# Contains the message text.
Message = ‘’
# Determines when the content is a message.
IsMessage = False
# Check for the kind of element before processing it.
def startElement(self, name, attrs):
if name == ‘Message’:
self.IsMessage = True
self.Message = ‘’
else:
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self.IsMessage = False
# If this is the right kind of element, display the message for it.
def endElement(self, name):
if name == ‘Message’:
print ‘Message:’, self.Message.strip(‘\n\t’)
# Add each of the characters of the message to the Message variable.
def characters(self, ch):
if self.IsMessage:
self.Message += ch
# Create a parser.
Parser = xml.sax.make_parser()
# Create a handler for the parser and tell the parser to use it.
Handler = MessageHandler()
Parser.setContentHandler(Handler)
# Open a source and parse it using the parser with the custom handler.
Parser.parse(open(‘Test2.XML’))
# Pause after the debug session.
raw_input(‘\nPress any key to continue...’)
The code begins by importing the required 
xml.sax
module. You don’t need anything fancy to create a 
basic SAX handler. Remember that SAX processes the file one character at a time and generates events 
based on the characters that the parser sees. Consequently, the code may seem a little odd for someone 
who is used to working with complete elements, but SAX gives you fine control over the processing 
cycle, including locating errors within the file.
The centerpiece of this example is the 
MessageHandler
class. This class includes a variable to hold 
the message (
Message
), an indicator of whether an element is a message (
IsMessage
), and the three 
methods described in the following list.
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