creating a similar object from an derived class

[Scott]

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