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')