class Publisher:
  def __init__(self):
    pass
  def register(self):
    pass
  def unregister(self):
    pass
  def notifyAll(self):
    pass
class TechForum(Publisher):
  def __init__(self):
    self._listOfUsers = []
    self.postname = None
  def register(self, userObj):
    if userObj not in self._listOfUsers:
      self._listOfUsers.append(userObj)
  def unregister(self, userObj):
    self._listOfUsers.remove(userObj)
  def notifyAll(self):
    for objects in self._listOfUsers:
      objects.notify(self.postname)
  def writeNewPost(self , postname):
    self.postname = postname
    self.notifyAll()
class Subscriber:
  def __init__(self):
    pass
  def notify(self):
    pass
class User1(Subscriber):
  def notify(self, postname):
    print "User1 notified of a new post %s" % postname
class User2(Subscriber):
  def notify(self, postname):
    print "User2 notified of a new post %s" % postname
class SisterSites(Subscriber):
  def __init__(self):
    self._sisterWebsites = ["Site1" , "Site2", "Site3"]
  def notify(self, postname):
    for site in self._sisterWebsites:
        print "Send nofication to site:%s " % site
if __name__ == "__main__":
  techForum = TechForum()
  user1 = User1()
  user2 = User2()
  sites = SisterSites()
  techForum.register(user1)
  techForum.register(user2)
  techForum.register(sites)
  techForum.writeNewPost("Observe Pattern in Python")
  techForum.unregister(user2)
  techForum.writeNewPost("MVC Pattern in Python")