dynamic class instantiation

[Ognen Duzlevski]

Larry Bates <larry.bates at websafe.com> wrote:
> > Now I want to use something like xml.dom.minidom to "parse" the 
> > .xml file into a set of classes defined according to the "language 
> > definition" file. The parse() method from the xml.dom.minidom 
> > package will return a document instance and I can get the node 
> > name from it. Say I got "page" as a string. How do I go about 
> > instantiating a class from this piece of information? To make it 
> > more obvious how do I create the page() class based on the "page" 
> > string I have? I want to make this generic so for me the language 
> > definition file will contain pages, functions, datasets etc. but 
> > for someone else mileage will vary.
> > 
> > Thanks,
> > Ognen

> I think you should rethink this approach.  Why have 3 different
> files instead of just defining everything as Python classes?
> Get good baseclass definitions and use OOP inheritance to
> create your specific class instances.  I think mixing XML,
> language definition file (LDF), LDF to python parser is a LOT
> harder (and slower) than just writing the classes outright.

Hi Larry,

here is the whole story. I have a database (postgres) xml "transformer"
and substitution engine. It is written entirely in plpgsql and the whole 
environment works something like this. Someone writes an xml file that
defines a web page. This xml file is then fed into the database at the
time of development. Now at runtime a mod_python apache webapp makes a 
request for a certain page. Its xml form is retrieved from the database
and a lot of data substitution goes on. Also parts of the page are "masked"
out by the database engine based on the "level" of the person requesting
the page. The "transformed and substituted" xml is then spit back to the 
webapp which now applies an xml->html transformation and presents the
final result to the user. So, I want people to be able to "define" their
own "language" when it comes to page definitions. And instead of rewriting
the xml file parser I want to be able to generate the parser.

Thanks,
Ognen