[Python-ideas] dict.merge(d1, d2, ...) (Counter proposal for PEP 584)

Antoine Pitrou solipsis at pitrou.net
Thu Mar 21 10:43:34 EDT 2019

On Tue, 5 Mar 2019 16:39:40 +0900
INADA Naoki <songofacandy at gmail.com>
> I think some people in favor of PEP 584 just want
> single expression for merging dicts without in-place update.
> But I feel it's abuse of operator overload.  I think functions
> and methods are better than operator unless the operator
> has good math metaphor, or very frequently used as concatenate
> strings.
> This is why function and methods are better:
> * Easy to search.
> * Name can describe it's behavior better than abused operator.
> * Simpler lookup behavior. (e.g. subclass and __iadd__)
> Then, I propose `dict.merge` method.  It is outer-place version
> of `dict.update`, but accepts multiple dicts.  (dict.update()
> can be updated to accept multiple dicts, but it's not out of scope).
> * d = d1.merge(d2)  # d = d1.copy(); d.update(d2)

One should also be able to write `d = dict.merge(d1, d2, ...)`

If dict merging is important enough to get a new spelling, then I think
this proposal is the best: explicit, unambiguous, immediately
understandable and easy to remember.



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