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About the implementation of del in Python 3

On Fri, Jul 7, 2017 at 9:48 PM, Marko Rauhamaa <marko at pacujo.net> wrote:
> Chris Angelico <rosuav at gmail.com>:
>> On Fri, Jul 7, 2017 at 7:15 PM, Marko Rauhamaa <marko at pacujo.net> wrote:
>>> You can only define the semantics of Python (in this case) by
>>> providing an *arbitrary* mapping to an imaginary abstract machine.
>>> There's no way to define the objective abstraction.
>> So aside from an artificial sense of purity, what's the point in
>> defining object identity *at all*? Why invent an arbitrary number that
>> you can't even see?
> Without such an invisible identity, you can't specify the desired
> behavior of a Python program. (Well, id() returns a visible identity,
> which you could equate with the invisible one.)
> I understand that not everything should be strictly formal, but all
> attempts at clarifying Python's object system necessarily involve
> evoking some silly abstract model.

"x is y" returns True if and only if x and y refer to the same object.

You have yet to demonstrate that the above statement is underspecified.