creating a similar object from an derived class

Matimus mccredie at gmail.com
Wed Sep 3 21:51:32 CEST 2008


On Sep 3, 12:09 pm, Scott <smba... at gmail.com> wrote:
> Let's say I have an object:
>
> class foo():
>    def create_another()
>        return foo()
>
>    def blah():
>        x = self.create_another()
>        ... do something with X
>
> Now I create a inherited class of this object:
>
> class bar(foo):
>     ...
>
> If I call bar.create_another(), it will return a foo() instead of a
> bar(). This isn't what I want. I would like bar.create_another() to
> create an instance for bar(). Obviously I can do this by overriding
> create_another, i.e.
>
> class bar(foo):
>     def create_another()
>         return bar()
>
> However, is there a way for me to modify foo() so that it
> automatically creates objects of the derived class, so that I don't
> have to continue to redefine create_another() ?
>
> For example, I tried the following:
>
> def create_another()
>     return self.type()()
>
> but it did not work.
>
> Thanks,
> Scott

This works:

>>> class C(object):
...   @classmethod
...   def create_another(cls):
...       return cls()
...
>>> class D(C):
...   pass
...
>>> d = D()
>>> e = d.create_another()
>>> isinstance(e, D)
True


Matt



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