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    This seems like a bad idea. You want a Singleton, but it can be one of 3 things? Could you add a little more information on the motivation behind doing this? Commented Jan 25, 2014 at 21:49
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    Short answer - you don't. One commonly repeated statement about Python is "we're all consenting adults here." Don't try to restrict what people can do with your classes (e.g. how many instances they create of one class) - just make sure you tell them what they should do. If they do something you have recommended that they don't do and stuff goes wrong then it is their own fault. Commented Jan 25, 2014 at 21:49
  • There is an example in the design pattern text book which is about a MazeFactory Singleton object. The MazeFactory has two subclasses BombedMazeFactory and EnchantedMazeFactory. An application can only have 1 maze factory object which can be any of the above three. C++ implementation can enforce this restriction. But I don't know how Python can do this. Commented Jan 25, 2014 at 21:53
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    Take look at the answers to "Creating a singleton in python" or just "share global variables across modules" Commented Jan 25, 2014 at 22:02
  • If you want to create independent singleton classes, I suggest you use a singleton decorator instead of inheritance. Commented Jan 25, 2014 at 22:31