adapter.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""http://ginstrom.com/scribbles/2008/11/06/generic-adapter-class-in-python/"""

import os

class Dog(object):
 def __init__(self):
 self.name = "Dog"
 def bark(self):
 return "woof!"

class Cat(object):
 def __init__(self):
 self.name = "Cat"
 def meow(self):
 return "meow!"

class Human(object):
 def __init__(self):
 self.name = "Human"
 def speak(self):
 return "'hello'"


class Car(object):
 def __init__(self):
 self.name = "Car"
 def make_noise(self, octane_level):
 return "vroom{0}".format("!" * octane_level)


class Adapter(object):

 """
 Adapts an object by replacing methods.
 Usage:
 dog = Dog
 dog = Adapter(dog, dict(make_noise=dog.bark))

 >>> objects = []
 >>> dog = Dog()
 >>> objects.append(Adapter(dog, dict(make_noise=dog.bark)))
 >>> cat = Cat()
 >>> objects.append(Adapter(cat, dict(make_noise=cat.meow)))
 >>> human = Human()
 >>> objects.append(Adapter(human, dict(make_noise=human.speak)))
 >>> car = Car()
 >>> car_noise = lambda: car.make_noise(3)
 >>> objects.append(Adapter(car, dict(make_noise=car_noise)))

 >>> for obj in objects:
 ... print('A {} goes {}'.format(obj.name, obj.make_noise()))
 A Dog goes woof!
 A Cat goes meow!
 A Human goes 'hello'
 A Car goes vroom!!!
 """

 def __init__(self, obj, adapted_methods):
 """We set the adapted methods in the object's dict"""
 self.obj = obj
 self.__dict__.update(adapted_methods)

 def __getattr__(self, attr):
 """All non-adapted calls are passed to the object"""
 return getattr(self.obj, attr)


def main():
 objects = []
 dog = Dog()
 objects.append(Adapter(dog, dict(make_noise=dog.bark)))
 cat = Cat()
 objects.append(Adapter(cat, dict(make_noise=cat.meow)))
 human = Human()
 objects.append(Adapter(human, dict(make_noise=human.speak)))
 car = Car()
 objects.append(Adapter(car, dict(make_noise=lambda: car.make_noise(3))))

 for obj in objects:
 print("A {0} goes {1}".format(obj.name, obj.make_noise()))


if __name__ == "__main__":
 main()

### OUTPUT ###
# A Dog goes woof!
# A Cat goes meow!
# A Human goes 'hello'
# A Car goes vroom!!!