Example strategy pattern in Python

StrategyPattern.py

import math

class Metric(object):
	"""Abstract class"""
	def distance(self,x,y):
		raise NotImplementedError("Derived classes should implement this.")

class EuclideanMetric(Metric):
	"""Calculates distance from origin in R according to Pythagorean distance"""
	def distance(self,x,y):
		return math.sqrt(x*x+y*y)

class ManhattanMetric(Metric):
	"""Calculates distance from origin in R according to Manhattan Metric"""
	def distance(self,x,y):
		return abs(x)+abs(y)

class Consumer(Metric):
	"""We can use this class to use either of the two metrics"""
	def __init__(self, arg):
		self.metric = arg()

	def distance(self,x,y):
		return self.metric.distance(x,y)

euclid = Consumer(EuclideanMetric)
print(euclid.distance(3,4))

manhattan = Consumer(ManhattanMetric)
print(manhattan.distance(1,-2))

###### Raises NotImplementedException
#error = Metric(object)
#print(error.distance(1,2))