[Python-Dev] ElementTree in stdlib (original) (raw)

Walter Dörwald walter at livinglogic.de
Wed Dec 14 09:04:43 CET 2005

Guido van Rossum wrote:

On 12/13/05, Walter Dörwald <walter at livinglogic.de> wrote:

Guido van Rossum wrote:

I don't think that SAX is unpythonic, but it's pretty low-level and mostly of use to people writing higher-level XML parsers (my parsexml module uses it). Having to define classes that conform to a certain API and registering instances of those classes as callbacks with the parser doesn't look that pythonic to me. An iterator API seems much more pythonic. Perhaps. Although the SAX API lets you leave a callback undefined if you don't have a need to handle those events; that's a bit trickier to do with an iterator.

Changing the iterator to only generate the events you need requires passing information to the iterator. And when you do that you can just as well pass information about which function to call at which event.

But IMHO the main difference isn't dispatching, but who's in control.

Also the different callbacks have different signatures.

True, I've always wondered why SAX uses a startelement callback which gets passed a complete attribute dictionary. IMHO for spam the following event sequence would be better:

starttagbegin foo attributebegin bar text baz attributeend bar starttagend foo text spam endtag foo

This would simplify signatures (always one string argument) and it would leave handling entity references inside attribute values to the application (or at least a higher level of the parser).

But since /F solved this for ElementTree I have to mostly agree with you. :-)

Unfortunately there probably won't be that many parsers that support iterparse(). Most parsers existing outside the Python world use the callback model and turning a callback parser into a iterator parser requires support for incremental parsing (which has a certain latency) or stack switching tricks.

Then again, pythonic is whatever you say that it is. ;) Not at all. I will argue but I will also take arguments from others. Seriously.

Bye, Walter Dörwald

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