Changing base class in a inheritance hierarchy

Question

I have a class structure like

class A:
    def method1(self):
        return 1

class B:
    def method2(self):
        return 2

class C(A,B):
    def method3(self):
        return self.method1()+self.method2()

The Classes A and B provide functionality which class C gathers and enriches with some wrappers. Now it happens that I need a similar class C2 which is derived from a different implementation A2 instead of A: class C2(A2, B) with the same method3.

How would you realize such a design (C can derive from different implementation classes)?

If it has to do with advanced Python programming (meta-classes?) an example would be appreciated :)

It's not clear what you're asking. If you need another class that inherits from a different base class, just define your new class so it inherits from that base class. — BrenBarn
– BrenBarn, Commented Jun 20, 2012 at 19:31

Jochen Ritzel · Accepted Answer · 2012-06-20 19:32:37Z

4

class CMixin:
    def method3(self):
        return self.method1()+self.method2()

class C1(A,B, CMixin):
    pass

class C2(A2,B, CMixin):
    pass

Though the design you describe sounds like you want aggregation instead:

class C:
    def __init__(self, a, b):
        self.a = a
        self.b = b

    def method3(self):
        return self.a.method1() + self.b.method2()


c1 = C(a1, b)
c2 = C(a2, b)

answered Jun 20, 2012 at 19:32

Jochen Ritzel

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2 Comments

Gareth Latty Over a year ago

This was my first thought. Simple is better.

Gere Over a year ago

Oh. Somehow I wasn't aware that I can use methods that aren't in the base classes yet :)

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