Python Observer

Observer.py

from Subscriber import *

class Observer:
	subscribersList = []

	def subscribe(self,subscriber):
		try:
			if self.isAllowedSubscriber(subscriber):
				if self.uniqueIdValidation(subscriber.id):
					self.subscribersList.append(subscriber)
					return True
				else:
					return False;
			else:
				return False
		except Exception as ex:
			print ex;
			return False

	def unsubscribe(self,id):
		try:
			for subscriber in self.subscribersList:
				if subscriber.id ==id:
					self.subscribersList.remove(subscriber)

			return True
		except Exception as ex:
			print ex;
			return False

	def publish(self, publishNotification):
		for subscriber in self.subscribersList:
			subscriber.receiveNotification(publishNotification)

	def isAllowedSubscriber(self,subscriber):
		return isinstance(subscriber,Subscriber)

	def uniqueIdValidation(self,id):
		if len(self.subscribersList) !=0:
			for subscriber in self.subscribersList:
				if subscriber.id == id:
					return False
				else:
					return True
		else:
			return True

ObserverTests.py

from Subscriber import *
from Observer import *
class ObserverTests:
	SUCCESS_MESSAGE="OK"
	ERROR_MESSAGE = "ERROR"
	observer = Observer()


	def test_addAllowedSubscriber(self):
		try:
			subscriber = Subscriber();
			subscriber.id = "sub_01"
			
			
			isSubscriberAdded = self.observer.subscribe(subscriber)
			if isSubscriberAdded & len(self.observer.subscribersList)>0:
				return self.SUCCESS_MESSAGE
			else:
				return self.ERROR_MESSAGE
		except Exception as ex:
			print ex
			return self.ERROR_MESSAGE


	def test_addAllowedSubscriberTwice(self):
		try:
			subscriber = Subscriber();
			subscriber.id = "sub_01"

			subscriber2 = Subscriber();
			subscriber2.id = "sub_01"

			isSubscriberAdded_1 = self.observer.subscribe(subscriber)
			isSubscriberAdded_2 = self.observer.subscribe(subscriber2)

			if (not isSubscriberAdded_2) & len(self.observer.subscribersList)==1:
				return self.SUCCESS_MESSAGE
			else:
				return self.ERROR_MESSAGE
		except Exception as ex:
			print ex
			return self.ERROR_MESSAGE


	def test_addNotAllowedSubscriber(self):
		try:
			subscriberFalse = "sub_02"
			isSubscriberAdded = self.observer.subscribe(subscriberFalse)
			if (not isSubscriberAdded) & len(self.observer.subscribersList)==1:
				return self.SUCCESS_MESSAGE
			else:
				return self.ERROR_MESSAGE
		except Exception as ex:
			print ex
			return self.ERROR_MESSAGE



	def test_RemoveSubscriber(self):
		try:
			subscriber = Subscriber();
			subscriber.id = "sub_01"
			self.observer.subscribe(subscriber)
			isSubscriberRemoved =self.observer.unsubscribe("sub_01") 
			if isSubscriberRemoved & len(self.observer.subscribersList)==0:
				return self.SUCCESS_MESSAGE
			else:
				return self.ERROR_MESSAGE
		except Exception as ex:
			print ex
			return self.ERROR_MESSAGE



	def test_publish(self):
		try:
			subscriber = Subscriber();
			subscriber.id = "sub_01"
			subscriber2 = Subscriber();
			subscriber2.id = "sub_02"

			self.observer.subscribe(subscriber)
			self.observer.subscribe(subscriber2)

			notification= "notification!"
			self.observer.publish(notification)
			return self.SUCCESS_MESSAGE

		except Exception as ex:
			print ex
			return self.ERROR_MESSAGE

observerTests = ObserverTests()
result={}
result["add allowed Subscriber"]= observerTests.test_addAllowedSubscriber()
result["add not allowed Subscriber"]= observerTests.test_addNotAllowedSubscriber()
result["Adding a subscriber with an existing id "] = observerTests.test_addAllowedSubscriberTwice()
result["remove Subscriber"]= observerTests.test_RemoveSubscriber()
result["publish"]= observerTests.test_publish()

print "Test results:------------------------"
for key,value in result.iteritems():
	print key,"---" ,value;

Subscriber.py

class Subscriber:
	id=""
	def receiveNotification(self,publishNotification):
		#Do something with the publish notification...
		#here you can put some  default business rule, that aplies for all Subscribers
		print self.id,"-",publishNotification