Creating a singleton container class for intrer-class messaging

Question

My question is for validation of my code (any loop holes / bugs) and guidance the best methodology to implement for my requirement.

I am developing a Python application that will have many classes. We need to communicate in between each class - pass data. It would be very clumsy if across all classes I create a setter/getter method and refer them across different classes, hence I prefer to pass a container object in between all of them:

class One
 def __init__(self, container):
class Two
 def __init__(self, container):

Now obviously I want that this container object should be a Singleton object - only one instance to pass multiple data structures. Below is my code for same [class declaration for Container class]:

import abc
class Container(object):
 __metaclass__ = abc.ABCMeta
 __data1 = 0
 __data2 = 0
 @abc.abstractmethod
 def dummy():
 raise NotImplementedError()
 def __init__(self):
 self.__data1 = 0
 self.__data2 = 1
 def SetData(self,value):
 self.__data1 = value
 def GetData(self):
 return self.__data1
class Singleton(Container):
 _instances = {}
 def __new__(class_, *args, **kwargs):
 if class_ not in class_._instances:
 class_._instances[class_] = super(Singleton, class_).__new__(class_, *args, **kwargs)
 return class_._instances[class_]
 def dummy():
 pass

Now in my application, I would not be able to create an another separate instance of Container [abstract class] / Singleton class. So I can pass the object of Singleton like as mentioned below:

class One:
 def __init__(self, container)
 self.value = container.GetData()
 ................................
 container.SetData(9)
 Two(container)
class Two:
 def __init__(self, container)
 self.value = container.GetData()
 ................................
 container.SetData(19)
 ................................
class Three:
 def __init__(self, container)
 self.container = Singleton()
 ................................
 container.GetData() # will return value 19 only
 container.SetData(19)
 ................................
if __name__ == "__main__":
 container = Singleton()
 container.SetData(9)
 One(container)

Please comment on my approach and modifications required if any. This code will be pushed in production box - so I want to double check my implementation.

Answer 1

I don't see why you need a singleton. You are already passing around container references as parameters. So, if you only create one container in __main__ and pass that to the class instances, they will all be accessing the same container.

Instead of calling Singleton() in Three.__init__ you would simply do the usual thing:

class Three:
 def __init__(self, container)
 self.container = container