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[Python-Dev] Need discussion for a PR about memory and > objects


> Date: Sun, 18 Nov 2018 22:32:35 +1000
> From: Nick Coghlan <ncoghlan at gmail.com>
> To: "Steven D'Aprano" <steve at pearwood.info>
> Cc: python-dev <python-dev at python.org>
> Subject: Re: [Python-Dev] Need discussion for a PR about memory and
>         objects

[  munch background ]
>
> Chris's initial suggestion was to use "license number" or "social
> security number" (i.e. numbers governments assign to people), but I'm
> thinking a better comparison might be to vehicle registration numbers,
> since that analogy can be extended to the type and value
> characteristics in a fairly straightforward way:
>
> - the object identity is like the registration number or license plate
> (unique within the particular system of registering vehicles, but not
> unique across systems, and may sometimes be transferred to a new
> vehicle after the old one is destroyed)
> - the object type is like the make and model (e.g. a 2007 Toyota
> Corolla Ascent Sedan)
> - the object value is a specific car (e.g. "that white Corolla over
> there with 89000 km on the odometer")
>
> On the other hand, we're talking about the language reference here,
> not the tutorial, and understanding memory addressing seems like a
> reasonable assumed pre-requisite in that context.

"Handle" has been used since the 1980s among Macintosh and
Win32 programmers as "unique identifier of some object but isn't
the memory address". The usage within those APIs seems to
match what's being proposed for the new Python C API, in that
programmers used functions to ask "what type are you?" "what
value do you have?" but couldn't, or at least shouldn't, rely on
actual memory layout.

I suggest that for the language reference, use the license plate
or registration analogy to introduce "handle" and after that use
handle throughout. It's short, distinctive, and either will match
up with what the programmer already knows or won't clash if
or when they encounter handles elsewhere.

-- 

        cheers,
        Hugh Fisher