[Python-Dev] Proposal: dict.with_values(iterable)
steve.dower at python.org
Mon Apr 22 22:27:43 EDT 2019
On 22Apr2019 1921, Steve Dower wrote:
> On 22Apr2019 1822, Glenn Linderman wrote:
>> Inada is now proposing a way to allow the coder to suggest a group of
>> dictionaries that might benefit from the same gains, by preclassifying
>> non-__dict__ slot dictionaries to do similar sharing.
>> CSV reader is an exemplary candidate, because it creates groups of
>> dicts that use the same keys. (column names). I have other code that
>> does similar things, that would get similar benefits.
>> Seems like since it is just an interface to existing builtin code,
>> that the one interface function (or dictionary factory class) could
>> just as well be a builtin function, instead of requiring an import.
> Sounds like a similar optimisation to sys.intern() is for strings.
> I see no reason to try and avoid an import here - it's definitely a
> special-case situation - but otherwise having a function to say "clone
> and update this dict" that starts by sharing the keys in the same way
> that __dict__ does (including the transformation when necessary) seems
> like an okay addition. Maybe copy() could just be enabled for this?
Or possibly just "dict(existing_dict).update(new_items)".
My primary concern is still to avoid making CPython performance
characteristics part of the Python language definition. That only makes
it harder for alternate implementations. (Even though I was out-voted
last time on this issue since all the publicly-known alternate
implementations said it would be okay... I'm still going to put in a
vote for avoiding new language semantics for the sake of a single
runtime's performance characteristics.)
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