Professional IronPython

Working with xml.sax
It’s important to remember that SAX is an event-driven method of working with XML. An applica-
tion looks at a small number of bits out of an entire document. Consequently, SAX can be a good 
FIgURE 13-6: 
The Python output is similar, but not precisely 
the same as the .NET output.
548592c13.indd 283
2/24/10 12:48:59 PM
www.finebook.ir

---

284
❘
CHAPTER 13
Working With XML Data
method for processing larger documents that you can’t read into memory at one time. A SAX appli-
cation normally relies on three constructs:
➤
One or more sources as input
➤
A parser (normally, only one is used)
➤
➤
One or more handlers to respond to input events
➤
➤
There are many different Python SAX modules. Each of these modules provides different imple-
mentations of the three constructions. The default SAX implementation provides just four handlers. 
These handlers are implemented as classes that you use to interact with the events generated by the 
input file.
➤➤
ContentHandler
: Provides the main SAX interface for handling document events. Most 
applications use this interface as a minimum because it provides the basic support required 
for any document. The example shows how to use this handler, which is provided as part of 
the 
xml.sax
module.
➤
➤
DTDHandler
: Manages all of the Document Type Definition (DTD) events.
➤
➤
EntityResolver
: Resolves external entities such as files referenced by processing 
instructions.
➤
➤
ErrorHandler
: Reports any errors or warnings that the parser encounters when it processes 
the XML. Provided as part of the 
xml.sax
module.
Now that you have a little better idea of what to expect, it’s time to look at an actual example. 
Listing 13-4 shows a simple SAX implementation that includes all of the constructs you normally 
need. Of course, you can easily add to this example to make it do considerably more than it does now.