public interface QuackBehavior {
    public void quack();
}
public class Quack implements QuackBehavior {
    public void quack() {
	System.out.println("Quacking Duck!");
    }
}
public class Squeak implements QuackBehavior {
    public void quack() {
	System.out.println("Squeaking Duck!");
    }
}
public class Duck {
    QuackBehavior quackBehavior;
    public void performQuack() {
	quackBehavior.quack();
    }
}
public class MallardDuck extends Duck {
    public MallardDuck() {
	quackBehavior = new Quack();
    }
}
Duck mallard = new MallardDuck();
mallard.performQuack();

class QuackBehavior:
    def quack():
        pass
class Quack(QuackBehavior):
    def quack(self):
        print("Quacking Duck!")
class Squeak(QuackBehavior):
    def quack(self):
        print("Squeaking Duck!")
class Duck:
    def performQuack(self):
        self.quackBehavior.quack()
    
class MallardDuck(Duck):
    def __init__(self):
        self.quackBehavior = Quack()
             
mallard = MallardDuck()
mallard.performQuack()

class Tqv1:
    def qv(self):
        print("krac")
class Tqv2:
    def qv(self):
        print("crac")
class Tsplash1:
    def sp(self):
        print("bum bum")
class Tsplash2:
    def sp(self):
        print("xlop xlop")
class Tdack1(Tqv1,Tsplash2):
    pass
class Tdack2(Tqv2,Tsplash1):
    pass
dack1=Tdack1()
dack2=Tdack2()
dack1.qv();
dack1.sp();
dack2.qv();
dack2.sp();
>>> 
krac
xlop xlop
crac
bum bum

class QuackBehavior:
    def quack():
        raise NotImplementedError