If a class Child inherits from Parent, how to implement Child.some_method if Parent.some_method() returns Parent instance ?

[metal]

On 10月30日, 下午4时44分, Bruno Desthuilliers <bruno.
42.desthuilli... at websiteburo.invalid> wrote:
> metal a écrit :
>
> > The actual situation is I'm coding with a immuable set-like datatype
> > XSet which supports XSet(['al']) & XSet(['ah'] = XSet(['ax']
>
> I assume it was '==', not '='
>
> > if I
> > declare ax is consists of al and ah
>
> > "That" means I can't explian it very well 'cause my english...
>
> > Now I try to make some mess like this...I know it's not good to wrap
> > all methods...I just try to make code looks good
>
> > class MyMeta(type):
> >     def __init__(cls, name, bases, namespace):
> >         type.__init__(cls, name, bases, namespace) # needed?
> >         cls.wrap_methods()
> >     def methods(cls):
> >         return [k for k, v in cls.__dict__.items() if callable(v)]
>
> All callables are not functions or methods... The inspect module might
> help you here.
>
> >     def wrap_methods(cls):
> >         for k in cls.methods():
> >             f = cls.__dict__[k]
>
> Just for the record, you wouldn't have to do this lookup if .methods
> returned the actual objects instead of their names) if callable(v)).
>
> >             def g(self, *v, **k):
> >                 rv = f(self, *v, **k)
> >                 if rv.__class__ is cls:
> >                     rv = self.__class__()
> >                     rv.__dict__.update(self.__dict__)
> >                 return rv
> >             setattr(cls, k, g)
>
> If you do have control over the whole class hierarchy, just write the
> base class so the alternate constructors return instances of the
> appropriate class. Else, manually wrapping the relevant methods would be
> a better solution IMHO. I'm not for premature optimization, but remember
> that method lookup and function call are two costly operations in
> Python, so better not adding too much overhead.

All code are just POCs. == or = doesn't matter :)

Sure I know .methods() can return actual objects if ONLY iteration,
but how to overwrite it?

type(self) in new-style class looks a little better, thanks for the
idea