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_ano ther()
... do something with X

Now I create a inherited class of this object:

class bar(foo):
...

If I call bar.create_anot her(), it will return a foo() instead of a
bar(). This isn't what I want. I would like bar.create_anot her() 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

[Matimus]

Re: creating a similar object from an derived class

On Sep 3, 12:09 pm, Scott <smba...@gmail. comwrote:

Let's say I have an object:
>
class foo():
   def create_another( )
       return foo()
>
   def blah():
       x = self.create_ano ther()
       ... do something with X
>
Now I create a inherited class of this object:
>
class bar(foo):
    ...
>
If I call bar.create_anot her(), it will return a foo() instead of a
bar(). This isn't what I want. I would like bar.create_anot her() 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_anothe r()
>>isinstance( e, D)

True


Matt

[MRAB]

Re: creating a similar object from an derived class

On Sep 3, 8:09 pm, Scott <smba...@gmail. comwrote:

Let's say I have an object:
>
class foo():
   def create_another( )
       return foo()
>
   def blah():
       x = self.create_ano ther()
       ... do something with X
>
Now I create a inherited class of this object:
>
class bar(foo):
    ...
>
If I call bar.create_anot her(), it will return a foo() instead of a
bar(). This isn't what I want. I would like bar.create_anot her() 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.
>

If you want a foo object to be able to create another foo object and a
bar object to be able to create another bar object then you could do
this:

class foo():
def create_another( self):
return self.__class__( )

class bar(foo):
pass