[Python-ideas] Adding "+" and "+=" operators to dict

[Chris Angelico]

On Fri, Feb 13, 2015 at 3:21 AM, Steven D'Aprano <steve at pearwood.info> wrote:
> On Fri, Feb 13, 2015 at 02:46:45AM +1100, Chris Angelico wrote:
>
>> Imagine if two people independently build shopping lists
>
> Sorry, was that shopping *lists* or shopping *dicts*?

I've never heard anyone in the real world talk about "shopping dicts"
or "shopping arrays" or "shopping collections.Sequences". It's always
"shopping lists". The fact that I might choose to represent one with a
dict is beside the point. :)

>> - "this is the stuff we need" - and
>> then combine them.
>
> Why would you discard duplicates? If you need 2 loaves of bread, and I
> need 1 loaf of bread, and the merged shopping list has anything less
> than 3 loaves of bread, one of us is going to miss out.
>

I live in a house with a lot of people. When I was younger, Mum used
to do most of the shopping, and she'd keep an eye on the fridge and
usually know what needed to be replenished; but some things she didn't
monitor, and relied on someone else to check them. If there's some
overlap in who checks what, we're all going to notice the same need -
we don't have separate requirements here. One person notes that we're
down to our last few eggs and should buy another dozen; another person
also notes that we're down to our last few eggs, but thinks we should
probably get two dozen. Getting *three* dozen is definitely wrong
here. And definitely her views on how much we should buy would trump
my own, as my experience was fairly minimal.

(These days, most of us are adult, and matters are a bit more
complicated. So I'm recalling "the simpler days of my youth" for the
example.)

ChrisA