First off, apologies for entering the discussion after it has formally
ended.
I'm not sure this has any relevance now that the PEP is accepted and the
reference implementation merged. If not, sorry and feel free to ignore.
"Leftmost Value (First-Seen) Wins" was rejected because
> it is not clear that this behavior has many use-cases
This is probably based on a thorough analysis of usage patterns, but the
result
still surprises me. I could not find the related discussion in the mail
archives. Could you elaborate, or point to more detailed information?
In my experience, the expression `value |= other` is a common idiom across
programming languages to provide a default for `value` if it is "unset".
For a
container-type, I would expect this operation, informally spoken, to be
applied
element-wise. In other words, the resulting dict would have the union of
keys,
with values supplied from `other` only if keys are missing in `value`.
This would allow users to provide defaults in a dictionary of settings, like
this:
settings |= defaults
As this usage generalizes a (perceived) common idiom, I would expect people
to
get bitten by this.
Claudio
On Mon, 17 Feb 2020 at 22:05, Guido van Rossum <gu...@python.org> wrote:
> Now that the last bits of discussion about PEP 584 have been settled (we
> will *not* be calling the `copy` or `update` methods) I am accepting this
> PEP. Congratulations Steven and Brandt!
>
> Thanks to everyone else who gave their opinion.
>
> Formally, I will just send my recommendation to accept the PEP to the
> Steering Council -- they will then let us know whether they agree, and once
> that's done we can update the PEP with the "Accepted" status and land the
> implementation (https://github.com/python/cpython/pull/12088). (Hm, the
> PEP should probably also link to that PR rather than to Brandt's private
> branch.)
>
> --
> --Guido van Rossum (python.org/~guido)
> *Pronouns: he/him **(why is my pronoun here?)*
> <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
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