Defining classes

[Nick Maclaren]

In article <mailman.1554.1166059503.32031.python-list at python.org>,
Michael Spencer <mahs at telcopartners.com> writes:
|> 
|> "instantiation" (i.e., calling the __new__ method) of new-style classes 
|> can return whatever you like, but I'm not sure how that helps.

Yes and no.  While it can return any value you like, it can't act as
a class declaration - and that is what I need in this context!  My
request in this thread was because I am trying to find a way around
that restriction.  All right, I am looking for a seriously advanced
language feature, that doesn't exist in 99% of known languages :-)

I am very much out of touch with Lisp, but there was an almighty
hoo-hah over this point some 25 years back, during the design of
Common Lisp.  I believe that it included it, and I am pretty sure
that I could do it in Haskell (which I am almost as out of touch
with), but in no other language that most people will ever have
heard of.  But I am (again) out of touch with this area!

Ideally, what I want to do is to define a class (A) in Python that
has essentially no exposed methods, but which can be instantiated to
produce another class (B), which can then be used exactly like a
built-in class (which is what it is designed to be).  Each such
instantiation of (A) would be a distinct class (B), derived from (A).
All of the methods of (B) would be inherited from 'hidden' methods
of (A), most would be in C (the language), and few would usable
directly on 'objects' of class (A).

There are several ways of doing this in Python, but I can't find
any that are as transparent to the user as I would really like.

There is method in my madness :-)


Regards,
Nick Maclaren.