Getting the super class via the super() function

[Fernando Rodriguez]

Hi,

I need to traverse the methods defined in a class and its superclasses. This
is the code I'm using:

# An instance of class B should be able to check all the methods defined in B
#and A, while an instance of class C should be able to check all methods
#defined in C, B and A.

#------------------------------------------------
class A(object):

def hasSuper(self,c ls):
if len(cls.mro()) > 1:
return 1
else:
return None


def traverse(self):
while self.hasSuper(s elf.__class__):
#do something
print 'Did something to a %s'%self
self = super(self.__cl ass__, self)

class B(A):
pass

class C(B):
pass

c = C()

c.traverse()
#-----------------------------------------------

I get this error:
while self.hasSuper(s elf.__class__):
AttributeError: 'super' object has no attribute 'hasSuper'

What am I doing wrong? I'm afraid that super isn't returning a reference to
the superclass... :-?

[Michael Hudson]

Re: Getting the super class via the super() function

Fernando Rodriguez <frr@easyjob.ne t> writes:
[color=blue]
> Hi,
>
> I need to traverse the methods defined in a class and its superclasses. This
> is the code I'm using:[/color]
[...]
[color=blue]
> What am I doing wrong? I'm afraid that super isn't returning a
> reference to the superclass... :-?[/color]

That's right, it's not. Python supports multiple inheritance -- what
is *the* superclass?

For new-style classes you're probably best off just looking through
cls.__mro__.

Cheers,
mwh

--
That's why the smartest companies use Common Lisp, but lie about it
so all their competitors think Lisp is slow and C++ is fast. (This
rumor has, however, gotten a little out of hand. :)
-- Erik Naggum, comp.lang.lisp

[Bob Willan]

Re: Getting the super class via the super() function

On Fri, 21 Nov 2003 17:29:24 +0100, Fernando Rodriguez wrote:
[color=blue]
> Hi,
>
> I need to traverse the methods defined in a class and its superclasses. This
> is the code I'm using:
>
> # An instance of class B should be able to check all the methods defined in B
> #and A, while an instance of class C should be able to check all methods
> #defined in C, B and A.
>[/color]
<snip>
I think the code below shows how to do what you want. It only prints the
inspect.classif y_class_attrs() to show that if you really want to, you can
determine which methods are created by each class vs. inherited from a
super class - e.g. __init__() in C vs inherited in D, traverse() in A vs
inherited in B, C, D.

Bob

[bob@localhost]$ cat xx.py
import inspect

class A(object):

def printobj(self):
print '\ninside A class object'


def traverse(self):
classes = inspect.getmro( self.__class__)
print classes
# get rid of last class, the 'object' class
classes = classes[:-1]
print classes
for c in classes:
members = inspect.getmemb ers(c,inspect.i smethod)
#do something
c.printobj(self )
print members
print
for a in inspect.classif y_class_attrs(c ):
print a
print '\n\n'

class B(A):
bb = 0
def printobj(self):
print '\ninside B class object'

class C(B):
aa = 0
def __init__(self):
self.c_only = 0

def printobj(self):
print '\ninside C class object'

class D(C):
def printobj(self):
print '\ninside D class object'

d = D()

d.traverse()

[bob@localhost]$ python xx.py
(<class '__main__.D'>, <class '__main__.C'>, <class '__main__.B'>, <class '__main__.A'>, <type 'object'>)
(<class '__main__.D'>, <class '__main__.C'>, <class '__main__.B'>, <class '__main__.A'>)

inside D class object
[('__init__', <unbound method D.__init__>), ('printobj', <unbound method D.printobj>), ('traverse', <unbound method D.traverse>)]

('__class__', 'data', <type 'object'>, <attribute '__class__' of 'object' objects>)
('__delattr__', 'method', <type 'object'>, <slot wrapper '__delattr__' of 'object' objects>)
('__dict__', 'data', <class '__main__.A'>, <attribute '__dict__' of 'A' objects>)
('__doc__', 'data', <class '__main__.D'>, None)
('__getattribut e__', 'method', <type 'object'>, <slot wrapper '__getattribute __' of 'object' objects>)
('__hash__', 'method', <type 'object'>, <slot wrapper '__hash__' of 'object' objects>)
('__init__', 'method', <class '__main__.C'>, <function __init__ at 0x80df154>)
('__module__', 'data', <class '__main__.D'>, '__main__')
('__new__', 'data', <type 'object'>, <built-in method __new__ of type object at 0x400d6a40>)
('__reduce__', 'method', <type 'object'>, <method '__reduce__' of 'object' objects>)
('__repr__', 'method', <type 'object'>, <slot wrapper '__repr__' of 'object' objects>)
('__setattr__', 'method', <type 'object'>, <slot wrapper '__setattr__' of 'object' objects>)
('__str__', 'method', <type 'object'>, <slot wrapper '__str__' of 'object' objects>)
('__weakref__', 'data', <class '__main__.A'>, <member '__weakref__' of 'A' objects>)
('aa', 'data', <class '__main__.C'>, 0)
('bb', 'data', <class '__main__.B'>, 0)
('printobj', 'method', <class '__main__.D'>, <function printobj at 0x80c6444>)
('traverse', 'method', <class '__main__.A'>, <function traverse at 0x8073e54>)

inside C class object
[('__init__', <unbound method C.__init__>), ('printobj', <unbound method C.printobj>), ('traverse', <unbound method C.traverse>)]

('__class__', 'data', <type 'object'>, <attribute '__class__' of 'object' objects>)
('__delattr__', 'method', <type 'object'>, <slot wrapper '__delattr__' of 'object' objects>)
('__dict__', 'data', <class '__main__.A'>, <attribute '__dict__' of 'A' objects>)
('__doc__', 'data', <class '__main__.C'>, None)
('__getattribut e__', 'method', <type 'object'>, <slot wrapper '__getattribute __' of 'object' objects>)
('__hash__', 'method', <type 'object'>, <slot wrapper '__hash__' of 'object' objects>)
('__init__', 'method', <class '__main__.C'>, <function __init__ at 0x80df154>)
('__module__', 'data', <class '__main__.C'>, '__main__')
('__new__', 'data', <type 'object'>, <built-in method __new__ of type object at 0x400d6a40>)
('__reduce__', 'method', <type 'object'>, <method '__reduce__' of 'object' objects>)
('__repr__', 'method', <type 'object'>, <slot wrapper '__repr__' of 'object' objects>)
('__setattr__', 'method', <type 'object'>, <slot wrapper '__setattr__' of 'object' objects>)
('__str__', 'method', <type 'object'>, <slot wrapper '__str__' of 'object' objects>)
('__weakref__', 'data', <class '__main__.A'>, <member '__weakref__' of 'A' objects>)
('aa', 'data', <class '__main__.C'>, 0)
('bb', 'data', <class '__main__.B'>, 0)
('printobj', 'method', <class '__main__.C'>, <function printobj at 0x80df18c>)
('traverse', 'method', <class '__main__.A'>, <function traverse at 0x8073e54>)

inside B class object
[('printobj', <unbound method B.printobj>), ('traverse', <unbound method B.traverse>)]

('__class__', 'data', <type 'object'>, <attribute '__class__' of 'object' objects>)
('__delattr__', 'method', <type 'object'>, <slot wrapper '__delattr__' of 'object' objects>)
('__dict__', 'data', <class '__main__.A'>, <attribute '__dict__' of 'A' objects>)
('__doc__', 'data', <class '__main__.B'>, None)
('__getattribut e__', 'method', <type 'object'>, <slot wrapper '__getattribute __' of 'object' objects>)
('__hash__', 'method', <type 'object'>, <slot wrapper '__hash__' of 'object' objects>)
('__init__', 'method', <type 'object'>, <slot wrapper '__init__' of 'object' objects>)
('__module__', 'data', <class '__main__.B'>, '__main__')
('__new__', 'data', <type 'object'>, <built-in method __new__ of type object at 0x400d6a40>)
('__reduce__', 'method', <type 'object'>, <method '__reduce__' of 'object' objects>)
('__repr__', 'method', <type 'object'>, <slot wrapper '__repr__' of 'object' objects>)
('__setattr__', 'method', <type 'object'>, <slot wrapper '__setattr__' of 'object' objects>)
('__str__', 'method', <type 'object'>, <slot wrapper '__str__' of 'object' objects>)
('__weakref__', 'data', <class '__main__.A'>, <member '__weakref__' of 'A' objects>)
('bb', 'data', <class '__main__.B'>, 0)
('printobj', 'method', <class '__main__.B'>, <function printobj at 0x80df11c>)
('traverse', 'method', <class '__main__.A'>, <function traverse at 0x8073e54>)

inside A class object
[('printobj', <unbound method A.printobj>), ('traverse', <unbound method A.traverse>)]

('__class__', 'data', <type 'object'>, <attribute '__class__' of 'object' objects>)
('__delattr__', 'method', <type 'object'>, <slot wrapper '__delattr__' of 'object' objects>)
('__dict__', 'data', <class '__main__.A'>, <attribute '__dict__' of 'A' objects>)
('__doc__', 'data', <class '__main__.A'>, None)
('__getattribut e__', 'method', <type 'object'>, <slot wrapper '__getattribute __' of 'object' objects>)
('__hash__', 'method', <type 'object'>, <slot wrapper '__hash__' of 'object' objects>)
('__init__', 'method', <type 'object'>, <slot wrapper '__init__' of 'object' objects>)
('__module__', 'data', <class '__main__.A'>, '__main__')
('__new__', 'data', <type 'object'>, <built-in method __new__ of type object at 0x400d6a40>)
('__reduce__', 'method', <type 'object'>, <method '__reduce__' of 'object' objects>)
('__repr__', 'method', <type 'object'>, <slot wrapper '__repr__' of 'object' objects>)
('__setattr__', 'method', <type 'object'>, <slot wrapper '__setattr__' of 'object' objects>)
('__str__', 'method', <type 'object'>, <slot wrapper '__str__' of 'object' objects>)
('__weakref__', 'data', <class '__main__.A'>, <member '__weakref__' of 'A' objects>)
('printobj', 'method', <class '__main__.A'>, <function printobj at 0x8073e1c>)
('traverse', 'method', <class '__main__.A'>, <function traverse at 0x8073e54>)