[Twisted-Python] Should I use asynchronous programming in my own modules?
itamar at itamarst.org
Thu Oct 18 09:09:39 EDT 2007
On Thu, 2007-10-18 at 14:41 +0200, Jürgen Strass wrote:
> I'm rather new to twisted and asynchronous programming in general.
> Overall, I think I've understood the asynchronous programming model and
> its implications quite well. Nevertheless, there are some remaining
> To give some example, I'd like to develop my own simplified document
> format in XML and a corresponding parser. The output of the parser (a
> specialized document object model) will be traversed and translated into
> HTML afterwards. This module could be useful outside any twisted
> application, of course. Instead of generating HTML one could develop a
> generator that produces LaTeX, for example. But it could also be used to
> render HTML pages in a twisted web application. The question is this:
> since parsing and generating large documents could block the reactor in
> a twisted app, should I use any of twisted's asynchronous programming
> features in this module (for better integration with twisted) or should
> I rather develop it in a traditional way and run it in a thread?
What you mean by "traditional" is actually a pull parser. Parsing APIs
can be pull or push (i.e. asynchronous). Well-designed parsers are
always push, because push parsers can be trivially converted to blocking
pull parsers, but not vice-versa. Some examples of push/asynch parsers:
twisted's Protocol class, or the SAX API.
The key difference: a pull parser will *read* data from some data source
with a blocking API. A push parser gets the data *pushed* to it by the
So: write a push parser. You won't need to use any Twisted facilities.
To make things a bit clearer - here's how you convert a push parser into
a pull parser:
parser = MyParser()
for line in f:
In Twisted, a push parser will often get data pushed to it from
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