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

Antoine Pitrou antoine at python.org
Fri Apr 15 05:01:00 EDT 2016

Victor Stinner <victor.stinner <at> gmail.com> writes:
> Hi,
> 2016-04-14 22:42 GMT+02:00 Armin Rigo <arigo <at> tunes.org>:
> > Hi Victor,
> >
> > On 14 April 2016 at 17:19, Victor Stinner <victor.stinner <at>
gmail.com> wrote:
> >> Each time a dictionary is created, the global
> >> version is incremented and the dictionary version is initialized to the
> >> global version.
> >
> > A detail, but why not set the version tag of new empty dictionaries to
> > zero, always?   Same after a clear().  This would satisfy the
> > condition: equality of the version tag is supposed to mean "the
> > dictionary content is precisely the same".
> You're right that incrementing the global version is useless for these
> specific cases, and using the version 0 should work. It only matters
> that the version (version? version tag?) is different.

Why do this? It's a nice property that two dicts always have different
version tags, and now you're killing this property for... no obvious

Do you really think dict.clear() is in need of micro-optimizing a
couple CPU cycles away?



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