Multi inheritance and design pattern

Question

In the facebook-python-business-sdk library, I've seen something that I thought it was bad practice :

AdAccountUserMixin 's get_pages() method uses self.iterate_edge() which is neither a method of this class nor a parent's.

AbstractCrudObject implements this method.

And then, AdAccountUser inherits from these two classes. That's why an object of AdAccountUser can use the method get_pages().

Minimal example :

class AbstractBar:
   def bar(self, x):
       return x

class Foo:
   def foo(self, x):
       return self.bar(x)

class Test(Foo, AbstractBar):
   def test(self, x):
       return self.foo(x)


t = Test()

t.test(5) # returns 5

Is this a design pattern, something that you see everyday or just a bad practice ?

Answer 1

That's quite ordinary mixin class stuff. A mixin class is a class that is explicitely designed to complement a given base class or interface (it explicitely relies on the class it's "mixed-in" with to implement a given interface). This is quite useful when you want to factor out some common behaviour from a bunch of classes that implement the same interface without having a common ancestor.