[Python-Dev] PEP 509: Add a private version to dict

[Maciej Fijalkowski]

On Wed, Jan 20, 2016 at 8:00 PM, Yury Selivanov <yselivanov.ml at gmail.com> wrote:
>
>
> On 2016-01-20 1:36 PM, Maciej Fijalkowski wrote:
>>
>> On Wed, Jan 20, 2016 at 7:22 PM, Brett Cannon <brett at python.org> wrote:
>>>
>>>
>>> On Wed, 20 Jan 2016 at 10:11 Yury Selivanov <yselivanov.ml at gmail.com>
>>> wrote:
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> [..]
>>>>
>>>> "ma_extra" would also make it easier for us to extend dicts
>>>> in the future.
>>>
>>>
>>> Why can't you simply use the id of the dict object as the globally unique
>>> dict ID? It's already globally unique amongst all Python objects which
>>> makes
>>> it inherently unique amongst dicts.
>>>
>>>
>> Brett, you need two things - the ID of the dict and the version tag.
>> What we do in pypy is we have a small object (called, surprisingly,
>> VersionTag()) and we use the ID of that. That way you can change the
>> version id of an existing dict and have only one field.
>
>
>
> Yeah, that's essentially what I propose with ma_extra.
>
> Yury

The trick is we use only one field :-)

you're proposing to have both fields - version tag and dict id. Why
not just use the id of the object (without any fields)?