Python: How to access parent class object through derived class instance?

Question

I'm sorry for my silly question, but... let's suppose I have this classes:

class A():
    msg = 'hehehe'

class B(A):
    msg = 'hohoho'

class C(B):
    pass

and an instance of B or C. So, how to get the variable 'msg' from the parent's class object through this instance? I've tried this:

foo = B() #or C()
bar = super(foo.__class__)
print bar.msg

but got the message: "TypeError: super() argument 1 must be type, not classobj"

Answer 1

Try with:

class A(object):
    msg = 'hehehe'

EDIT:

For the 'msg' attribute you would need:

foo = B()
bar = super(foo.__class__, foo)
print bar.msg

Answer 2

As msg is a class variable, you can just do:

print C.msg    # prints hohoho

If you overwrite the variable (as you do in class B), you have to find the right parent class. Remember that Python supports multiple inheritance.

But as you define the classes and you now that B inherits from A you can always do this:

class B(A):
    msg = 'hohoho'

    def get_parent_message(self):
       return A.msg

UPDATE:

The most reliable thing would be:

def get_parent_attribute(instance, attribute):
    for parent in instance.__class__.__bases__:
        if attribute in parent.__dict__:
             return parent.__dict__[attribute]

and then:

foo = B()
print get_parent_attribute(foo, 'msg')

Answer 3

foo = B()
print foo.__class__.__bases__[0].msg
// 'hehehe'

Answer 4

#for B() you can use __bases__
print foo.__class__.__bases__[0].msg

But this is not gonna be easy when there are multiple base classes and/or the depth of hierarchy is not one.

Answer 5

Not sure why you want to do this

>>> class A(object):
...     msg = 'hehehe'
... 
>>> class B(A):
...     msg = 'hohoho'
... 
>>> foo=B()
>>> foo.__class__.__mro__[1].msg
'hehehe'
>>> 

Answer 6

You actually want to use

class A(object):
    ...
...
b = B()
bar = super(b.__class__, b)
print bar.msg

Base classes must be new-style classes (inherit from object)