Alexander Belopolsky schrieb:

Changing the subject to reflect branched discussion and forwarding to python-ideas where it probably belongs.

On Mon, Oct 26, 2009 at 12:02 PM, Terry Reedy tjreedy@udel.edu wrote:

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Alexander Belopolsky wrote:

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Here is an alternative idea on how storing interned objects in a set can be supported. Currently set.add method returns None and has no effect when set already has an object equal to the one being added. I propose to consider changing that behavior to make set.add return the added object or the set member that is equal to the object being added. It is unlikely that many programs rely on the return value being None (with doctests being a probable exception), so adding this feature is unlikely to cause much grief.

I had exactly the same idea, but did not post because it violates the general rule that mutators return None.

Is there such a rule? What about set/dict pop?

The rule is about methods that do not have an obvious return value, where the choice is between returning self and None.

Georg