Strategy Pattern Blog: Code Snippets

example_2.py

# Flying Behavior
class FlyBehavior(object):
	def fly():
		raise NotImplementedError

class FlyWithWings(FlyBehavior):
	def fly():
		print "I am flying!"

class FlyNoWay(FlyBehavior):
	def fly():
		print "I can't fly"

# Quacking Behavior
class QuackBehavior(object):
	def quack():
		raise NotImplementedError

class Quack(QuackBehavior):
	def quack():
		print "Quack! Quack!"

class Squeak(QuackBehavior):
	def quack():
		print "Squeak! Squeak!"

class MuteQuack(QuackBehavior):
	def quack():
		print ":("

#
# And we integrate this with the `Duck` class and it's child classes
#

class Duck(object):
	...

	def __init__(self):
		self.fly_behavior = FlyBehavior()
		self.quack_behavior = QuackBehavior()

	def perform_fly():
		self.fly_behavior.fly()

	def perform_quack():
		self.quack_behavior.quack()

class MallardDuck(Duck):
	def __init__(self):
		self.fly_behavior = FlyWithWings()
		self.quack_behavior = Quack()

	def display():
		print "I look like a Mallard"

class RubberDuck(Duck):
	def __init__(self):
		self.fly_behavior = FlyNoWay()
		self.quack_behavior = Squeak()

	def display():
		print "I look like a Rubber Duck"