Returning other instance from __init__

[Paul Boddie]

On 15 Mar, 06:21, a... at mac.com (Alex Martelli) wrote:
> Paulo da Silva <psdasil... at esotericaX.ptX> wrote:
> >
> > I would like to implement something like this:
> >
> > class C1:
> >       def __init__(self,xxx):
> >               if ... :
> >                       self.foo = foo
> >                       self.bar = bar
> >               else:
> >                       self=C1.load(xxx)
> >
> >       def load(xxx):
> >               ...
> >               return instance_of_C1
> >       load=staticmethod(load)
> >
> > This does not seem correct. How can I do it?
>
> Use __new__ for such purposes, not __init__.  (You need to make C1
> newstyle, e.g. inherit from object, to make special method __new__
> work).

Call me a traditionalist, but why wouldn't a factory function be good
enough?

def C1(xxx):
    if ...:
        return the_real_C1()
    else:
        return load(xxx)

def load(xxx):
    ...
    return instance_of_C1

Or perhaps seeing more special methods and decorators just puts me in
a grumpy mood. ;-) For me, the power of Python is derived from being
able to do things like making callables "constructors" whilst
providing some illusion that C1 (in this case) is a class.

Paul