PEP 218 Re: ANN: set-0.1 module available

[Erik Max Francis]

"Denis S. Otkidach" wrote:

> There are still unresolved issues.  E.g. should set object be
> hashable?  Somebody wish sets of sets or set as dict key that
> require set to be hashable.

I would say yes, a set should require an immutable object, for the same
reason that a dictionary key should.  You couldn't have dictionaries
themselves as dictionary keys, and nobody seems to have a problem with
that.

I'm presuming that what's being considered is something close to the
mathematical definition of a set, where a set contains some number of
unique objects, in no defined order.  Adding an object to a set which
already contains it does nothing, since it can only be in the set at
most once.

A set can't contain an infinite number of objects -- although you could
create a proxy object that has the interface of a set and behaves like
it does.

I'm envisioning an implementation which behaves much like a dictionary,
with the elements of the set as keys, and with dummy values.  What's
wrong with that?

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