[Python-Dev] Retrieve an arbitrary element from a set without removing it

[Terry Reedy]

Guido van Rossum wrote:
> On Sat, Oct 24, 2009 at 10:34 AM, Alexander Belopolsky
> <alexander.belopolsky at gmail.com> wrote:
>> To me, however, a set seems to be a container that is a specialization
>> of a dict with values and keys being the same.
> 
> That's absurd; the mapping provides nothing useful.

Given Alexander's premise, I agree with your response. But his premise 
is wrong. Python's current builtin set class maps abstract equivalence 
classes to representative members. And this *is* useful. Mapping 
arbitrary members of such classes to representative members, sometimes 
called 'canonical', is a standard problem/goal in math. String interning 
is an application of this idea.

Terry Jan Reedy