The process of Singleton creation

# Singleton pattern(i.e., a class where only one instance is ever created)
class Singleton(type):
    def __init__(self, *args, **kwargs):
        self.__instance = None
        super().__init__(*args, **kwargs)

    def __call__(self, *args, **kwargs):
        if self.__instance is None:
            self.__instance = super().__call__(*args, **kwargs)
            return self.__instance
        else:
            return self.__instance

# Example
class Spam(metaclass=Singleton):
    def __init__(self):
        print('Creating Spam')


a = Spam()
b = Spam()
print(a is b)
c = Spam()
print(a is c)