+1. These would be handy for any iterable. It'll works on dict keys and values; bonus.

On Wed, 2021-10-06 at 15:42 +0100, Alex Waygood wrote:
Whether they are added to dict or itertools, there are still nine of 
them

No, the suggestion was to add two functions to itertools (first() and last(), which would work with any iterable, not just dicts), rather than adding nine methods to the dict interface. This was precisely why I was saying that I liked the itertools solution more.

On 6 Oct 2021, at 15:01, Steven D'Aprano <steve@pearwood.info> wrote:

On Wed, Oct 06, 2021 at 11:11:09AM +0100, Alex Waygood wrote:
The temptation to insist "see, YAGNI!" at this point I shall resist.

*You* might not need it, but I've seen it come up a lot on Stack
Overflow, and all too often people end up going for the much less
efficient solution. I personally have also written code with practical
applications using `next(iter(mydict))`.

Under what circumstances do you care what the first key in a dict is,
without going on to care about the second, third, fourth etc?

They are surely extremely niche, or artificial, or both, e.g. the
Stackoverflow problem you link to: "find the first non-repeating
character in a string -- using only one loop". Why the *first* rather
than any, or all?

In any case, the presence of one or two uses for a piece of
functionality doesn't mandate that we make this a builtin. Your solution
with next() is perfectly adequate.

The other suggested methods are even more obscure. Why have a method
for returning the first value, without knowing the key?

"I don't know what the first key is, and I don't care, but I know that
whatever it is, it maps to the value 17."

Now what are you going to do with that knowledge? This seems like a
method in desperate need of a use-case.


[...]
I agree that it's a lot of methods to add. That's precisely why I
prefer Inada Naoki's suggestion of additions to itertools

Whether they are added to dict or itertools, there are still nine of
them, and they are pretty much near clones of each other:

   # first_ and last_ whatsits
   next([iter|reversed](obj.[keys|values|items]()))

if you will excuse the misuse of hybrid Python/BNF syntax :-)



--
Steve
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