grids = {}

 def createGrid(name):

 	grids[name] = Grid(name)

 class Cell(object):

 	def __init__(self, id, value):

 		self.id = id

 		self.value = value

 	def __str__(self):

 		return "(id:%s value:%s)" % (self.id, self.value)

 class Grid(object):

 	def __init__(self, name):

 		self.name = name

 		self.cells = {}

 		self.observers = []

 	def set(self, cellId, value):		

 		if value and cellId not in self.cells:	

 			self.cells[cellId] = Cell(cellId, value)

 			self.dispatch(Cell(cellId, 0), self.cells[cellId])

 		elif not value and cellId in self.cells:

 			self.dispatch(self.cells[cellId], Cell(cellId, 0))

 			del self.cells[cellId]			

 	def dispatch(self, old, new):

 		for o in self.observers:

 			o[0].sendto("old: %s\nnew: %s\n" % (old, new), o[1])

 	def addObserver(self, socket, observer):

 		self.observers.append((socket, observer))