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... if you know for sure that Elvis has not yet been created, and that King has.

... if you know for sure that Elvis has not yet been created, and that King has*.

* some ontological issues here: could one singleton ever be another singleton? Subclassing a singleton class seems fraught with problems. And even then you'd probably be asking isinstance(), not is.

To make this complete you could also override __delattr__() to raise an Exception if an attempt is made to delete instance, and override __del__() so that it raises an Exception (unless we know the program is ending...)

... particularly (though not exclusively) if there is doubt concerning the pre-existence of Elvis and/or of that building.

To make this complete you could also override __delattr__() to raise an Exception if an attempt is made to delete instance, and override __del__() so that it raises an Exception (unless we know the program is ending...)

The singleton contract does not require that we be able to call the constructor multiple times. As a singleton should be created once and once only, shouldn't it be seen to be created just once? "Spoofing" the constructor arguably impairs legibility.

The singleton pattern does not require that we be able to call the constructor multiple times. As a singleton should be created once and once only, shouldn't it be seen to be created just once? "Spoofing" the constructor arguably impairs legibility.