«

Scott a écrit :
> Let's say I have an object:

s/object/class/

> class foo():
> def create_another()
> return foo()

class Foo(object):
def create_another(self):
return Foo()

> def blah():

def blah(self):
> x = self.create_another()
> ... do something with X

> Now I create a inherited class of this object:
>
> class bar(foo):

class Bar(Foo):
> ...
>
> If I call bar.create_another(), it will

Actually, it will raise a TypeError...

> 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().

def create_another(self)
return type(self)()


And while you're at it, since - at least in this concrete case - you
need access to the class but not to the instance, you could make it a
classmethod:

class Foo(object):
@classmethod
def create_another(cls):
return cls()


HTH

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

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

On Sep 3, 8:09*pm, Scott <smba...@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.
>
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