On Tue, Dec 3, 2019 at 2:00 AM Serhiy Storchaka <storch...@gmail.com> wrote:

> [SNIP]
> > ## What about performance?
>
> It should be mentioned in the PEP that `dict1 | dict2 | dict3` is less
> efficient than `{**dict1, **dict2, **dict3}`.
>

... in CPython, but is it guaranteed to be faster in e.g. PyPy? We should
be very careful about making any performance promises/points unless we know
it is fairly universal that the design will explicitly make something
faster or slower relative to another operation.

To me this PEP is entirely a question of whether the operators will
increase developer productivity and not some way to do dict merging faster,
and so performance questions should stay out of it unless it's somehow
slower than dict.update().
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