Lists implemented as integer-hashed Dictionaries?

Christian Heimes lists at
Sun Feb 8 14:38:25 EST 2009

Stephen Hansen schrieb:
> Now, I believe Python sets *are* for all intents and purposes
> dictionaries, but I think that's just because its the easiest and most
> efficient way to implement their uniqueness properties; they took the
> very-well-tuned dictionary implementation and cut out the stuff not
> needed by sets and did some tweaks here or there. I /believe/.

You are correct. The first set implementation in pure Python was using a
dict as internal storage. The new set implementation is heavily based on
the highly optimized dict code. Sets are basically dicts without values.

from Objects/setobject.c

   set object implementation
   Written and maintained by Raymond D. Hettinger <python at>
   Derived from Lib/ and Objects/dictobject.c.

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