class factory example needed (long)

[Gary Ruben]

Thanks for the very helpful reply Rainer,
I thought I couldn't use setattr because I need the syntactic sugar 
sqrt(f) to work, but with your example code Numeric.sqrt(f) does in fact 
work correctly. I also need to do a bit more than may be possible with a 
simple lambda function, but I should be able to sort it out from here 
with the info you provided,
thanks again,
Gary

Rainer Mansfeld wrote:
<snip>
> Hi Gary,
> 
> you want your 'class factory' to change the methods of Numeric, so that 
> they accept foo objects and return foo objects?
> I've not the slightest idea how to achieve that.
> 
> If OTOH you want your foo class to have sqrt, arccos, etc. methods 
> without defining them explicitly, I think you're looking for something 
> like:
> 
> . import Numeric
> .
> . class Foo(object):
> .     def __init__(self, value):
> .         self.value = float(value)
> .         for u in ['sqrt', 'cos', 'tan']:
> .             setattr(self, u, lambda uf=getattr(Numeric, u):
> .                                  uf(self.value + 42.0))
> 
>  >>> f = Foo(7)
>  >>> f.sqrt()
> 7.0
> 
> HTH
>   Rainer
>