dynamic

[James Carroll]

Returning instances of some other class is not so horrible.  They're
called FactoryMethods usually.

An example is when you have a polymorphic tree of image file reader
objects, and you open an image file, it might return a JpegReader
which ISA ImageReader or a TIFFReader which also ISA ImageReader, but
you want all of the 'which class do I need for  this data?' logic to
be in one place.

-Jim

On 15 Jun 2005 03:12:07 -0700, Michele Simionato
<michele.simionato at gmail.com> wrote:
> Having a class that returns instances
> of some other class is horrible, but
> since you asked for it:
> 
> class A(object): pass
> class B(object): pass
> 
> class Foo(object):
>     def __new__(cls, arg):
>         if arg=="a":
>             return A()
>         else:
>             return B()
> 
> print Foo("a")
> print Foo("b")
> 
>              Michele Simionato
> 
> P.S. don't do it!
> 
> --
> http://mail.python.org/mailman/listinfo/python-list
> 
>