Python Forum

Hi All,
I was trying to understand Inheritance concept in Python.
When I wrote the code without using super(), I was getting desired results. You can see that below

class Base1(object):
    def __init__(self):
        self.name1 = "Peter"

    def showName1(self):
        print(self.name1)

class Base2(object):
    def __init__(self):
        self.name2 = "John"

    def showName2(self):
        print(self.name2)

class Child(Base2, Base1):
    def __init__(self):
        self.name3 = "Sagar"
        Base1.__init__(self)
        Base2.__init__(self)
        

    def showName3(self):
        print(self.name3)

obj = Child()
obj.showName1()
obj.showName2()
obj.showName3()

Output:Peter
John
Sagar

But when I wrote super() in place of writing class name in Child class's __init__() function,

class Base1(object):
    def __init__(self):
        self.name1 = "Peter"

    def showName1(self):
        print(self.name1)

class Base2(object):
    def __init__(self):
        self.name2 = "John"

    def showName2(self):
        print(self.name2)

class Child(Base2, Base1):
    def __init__(self):
        self.name3 = "Sagar"
        super(Child,self).__init__()
        

    def showName3(self):
        print(self.name3)

obj = Child()
obj.showName1()
obj.showName2()
obj.showName3()

I am getting following error:

Error:Traceback (most recent call last):
  File "D:\Sagar\Python Related\Scripts\MultipleInheritance.py", line 25, in <module>
    obj.showName1()
  File "D:\Sagar\Python Related\Scripts\MultipleInheritance.py", line 6, in showName1
    print(self.name1)
AttributeError: 'Child' object has no attribute 'name1'

Is super() not used in case of Multiple Inheritance ?

(Sep-06-2017, 08:56 AM)Sagar Wrote: [ -> ]Is super() not used in case of Multiple Inheritance ?

I think the issue is all classes in the chain need to make the call to super, even if you think they are the last call.

Hide/Show

class Base1(object):
    def __init__(self):
        self.name1 = "Peter"
        super(Base1, self).__init__()
 
    def showName1(self):
        print(self.name1)

 
class Base2(object):
    def __init__(self):
        self.name2 = "John"
        super(Base2, self).__init__()
 
    def showName2(self):
        print(self.name2)


class Child(Base2, Base1):
    def __init__(self):
        self.name3 = "Sagar"
        super(Child, self).__init__()
         
    def showName3(self):
        print(self.name3)


obj = Child()
obj.showName1()
obj.showName2()
obj.showName3()

You should probably watch this video if you have not done so:
Super considered super

I was studying super() and its calling sequence of the Base and Sibling classes. I found that super is called in anticlockwise order and stops calling the next sibling or parent if there's no super() found in current class. I am sharing, what I found. Please correct me, if I am wrong.
Consider the following code

class A(object):
    def foo(self):
        print('A')

class B(A):
    def foo(self):
        print('B')
        super().foo()
 
class C(A):
    def foo(self):
        print('C')
        super().foo()
 
class D(B,C):
    def foo(self):
        print('D')
        super().foo()
 
d = D()
d.foo()

Here D inherits from the classes B and C and class A is the Base class of both classes B and C.
The output given by the above code is as follows:

Output:D
B
C
A

Now I included another class called "Foreign" in between and without super() like this:

class A(object):
    def foo(self):
        print('A')

class Foreign(object):
    def foo(self):
        print('Foreign')
        #super().foo()

class B(Foreign):
    def foo(self):
        print('B')
        super().foo()
 
class C(A):
    def foo(self):
        print('C')
        super().foo()
 
class D(B,C):
    def foo(self):
        print('D')
        super().foo()
 
d = D()
d.foo()

and the output for the above was:

Output:D
B
Foreign

Once I un-commented the super() of Foreign Class, the output was like this:

Output:D
B
Foreign
C
A

If I change the order of Base classes in the class definition of class D that is:
from

class D(B,C):

class D(C,B):

the order of calling super() also changes.
Note: There is no super in class A.

Sagar

Mekire

Sagar