[Python-ideas] PEP: Dict addition and subtraction
rosuav at gmail.com
Thu Mar 21 08:35:36 EDT 2019
On Thu, Mar 21, 2019 at 10:35 PM Antoine Pitrou <solipsis at pitrou.net> wrote:
> > but it's NOT a new operator, it is making use of an existing one, and sure
> > you could guess at a couple meanings, but the merge one is probably one of
> > the most obvious to guess, and one quick test and you know -- I really
> > can't see it being a ongoing source of confusion.
> Did you actually read what I said? The problem is not to understand
> what dict.__add__ does. It's to understand what code using the +
> operator does, without knowing upfront whether the inputs are dicts.
The + operator adds two things together. I don't understand the issue here.
You can add integers: 1 + 2 == 3
You can add floats: 0.5 + 1.25 == 1.75
You can add lists: [1,2] + [3,4] == [1,2,3,4]
You can add strings: "a" + "b" == "ab"
And soon you'll be able to add dictionaries. The exact semantics need
to be defined, but it's not fundamentally changing how you interpret
the + operator. I don't understand the panic here - or rather, I don't
understand why it's happening NOW, not back when lists got the ability
to be added (if that wasn't in the very first release).
Conversely, if it's the | operator, it's a matter of merging, and the
same is true. You can merge integers, treating them as bit sets. You
can merge sets. And now you'll be able to merge dictionaries. Same
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