[Python-Dev] RFC: PEP 509: Add a private version to dict (original) (raw)

Émanuel Barry vgr255 at live.ca
Thu Apr 14 17:00:58 EDT 2016

From Armin Rigo Sent: Thursday, April 14, 2016 4:42 PM To: Victor Stinner Cc: Python Dev Subject: Re: [Python-Dev] RFC: PEP 509: Add a private version to dict

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".

From Victor's original post:

"Globally unique identifier is a requirement for Yury's patch optimizing method calls ( https://bugs.python.org/issue26110 ). It allows to check for free if the dictionary was replaced."

I think it's a good design idea, and there's no chance that this counter will ever overflow (I think Victor is using 64-bit unsigned integer). I don't think there's really any drawback to using a global vs per-dict counter (but Victor is better placed to answer that :))

-Emanuel

Ducks lay where no programmer has ever been

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