super question

[Gonçalo Rodrigues]

Hi,

Ok, now I'm really confused. What is supposed

super(<class>, <subclass of class>)

to do?

My thought was that with the following setup:

class Test(object): .... def test(self):
.... return "I'm %r." % self
.... class Test2(Test): .... def test(self):
.... return "I'm a no one."
.... super(Test, Test2).test Traceback (most recent call last):
File "<interactive input>", line 1, in ?
AttributeError: 'super' object has no attribute 'test'

So far so good, object class (the super class of Test) defines no test
method so it barfs. But
super(Test2, Test2).test <bound method Test2.test of <class '__main__.Test2'>>

Huh? shouldn't it return the *unbound* method test at class Test? And
more:
a = Test2()
super(Test2, Test2).test(a) Traceback (most recent call last):
File "<interactive input>", line 1, in ?
TypeError: test() takes exactly 1 argument (2 given) super(Test2, Test2).test() "I'm <class '__main__.Test2'>."

A bug? Or my perceptions on what super(<class>, <subclass of class>)
should do are totally mixed up?

With my best regards,
G. Rodrigues

[Michael Hudson]

Gonçalo Rodrigues <op*****@mail.telepac.pt> writes:

Hi,

Ok, now I'm really confused. What is supposed

super(<class>, <subclass of class>)

to do?

My *guess* (and it is very much a guess) is that super(<class>,
<subclass of class>) is intended to be used in classmethods.

Cheers,
mwh

--
Wise frogs would take sanctuary in the cool moistness of the cat's
milk-dish, from where they would watch you. It's worrying being
watched by a milk-dish. -- Tanuki the Raccoon-dog, asr

[Harry Pehkonen]

Sorry -- Google is not letting me reply to the correct posting . . .

Aahz wrote:

but why not just do:

class C(B):
def meth(self, arg):
B.meth(self, arg)

Is there any difference?
Any advantage either way?

The advantage comes when you rename B or when you have multiple base
classes for C.

Like this?:

class C(A, B):
def __init__(self):
for parent in C.__bases__:
parent.__init__(self)

I don't think there is one definitive answer to the question of how to do this.

Harry.

[Terry Reedy]

"Harry Pehkonen" <ha************@hotpop.com> wrote in message
news:70**************************@posting.google.c om...

Aahz wrote:

but why not just do:

class C(B):
def meth(self, arg):
B.meth(self, arg)

Is there any difference?
Any advantage either way?

The advantage comes when you rename B or when you have multiple

base classes for C.

Like this?:

class C(A, B):
def __init__(self):
for parent in C.__bases__:
parent.__init__(self)

If A and B have common ancestor D, and both have code like either of
above, then above will result in two calls to D.__init__, once before
and once after B.__init__. I believe point of super mechanism is to
have D.__init__ called once at the proper time.

TJR