Interning own classes like strings for speed and size?

[Ulrich Eckhardt]

Steven D'Aprano wrote:
>>>> class InternedTuple(tuple):
> ...     _cache = {}
> ...     def __new__(cls, *args):
> ...             t = super().__new__(cls, *args)
> ...             return cls._cache.setdefault(t, t)

That looks good. The only thing that first bothered me is that it creates an 
object and then possibly discards it again. However, there is no way around 
that, since at least the key to the dict must be created for lookup. Since 
key and value are the same here, this is even for free.

What I also found was that with the above, I can't provide __eq__ and __ne__ 
that just check for identity. If I do, the lookup in setdefault() will never 
find an existing tuple and I will never save memory for a single object.


Thanks!

Uli