Feedback on Sets, and Partitions

[Andrew Koenig]

> I could live with only immutable sets, but it is nice
> being able to use:
>  myset.add(x)
>
> instead of:
>  newmyset = myset | Set([x])

What about

    myset |= Set([x])

Presumably that would work analogously to += for strings.

> Another unintutive feature is that there can be multiple sets with the
> same members. I.e., you can have sets A and B such that "A == B" is true
> and "A is B" is false.

Why is that any more unintuitive than the fact that there can be multiple
integers with the same value?
For example:

    x = 12345
    y = 12344+1

After these two statements, most Python implementations will evaluat "x is
y" as false, but of course 1==y is true.