I think there definitely should be a more obvious way to do this
(specifically the first and last keys/values/items of a dictionary — I'm
ambivalent about the others, since they won't always be fast, as discussed). An
anti-pattern you see quite often on Stack Overflow to get the first key of a
dictionary is something like the following:
first_key = list(mydict.keys())[0]
Whereas obviously, a much better way (especially if it's a very large
dictionary) is to do:
first_key = next(iter(mydict))
[Christopher Barker]
> I'll leave it exercise for the reader to find that thead
For reference, the (very long) previous thread is here:
https://mail.python.org/archives/list/[email protected]/thread/S7UMTWK65X6BJDYZ3SSU7I7HOIASDMMJ/.
[Inada Naoki]
> I think we can add `itertools.first()` for this idiom, and
> `itertools.last()` for `next(iter(reversed(x)))` idiom.
I like this idea, a lot. Another possibility I've been wondering about was
whether several methods should be added to the dict interface:
dict.first_key = lambda self: next(iter(self))
dict.first_val = lambda self: next(iter(self.values()))
dict.first_item = lambda self: next(iter(self.items()))
dict.last_key = lambda self: next(reversed(self))
dict.last_val = lambda self: next(reversed(self.values()))
dict.last_item = lambda self: next(reversed(self.items()))
But I think I like a lot more the idea of adding general ways of doing these
things to itertools.
Best,
Alex
> On 5 Oct 2021, at 05:30, Christopher Barker <[email protected]> wrote:
>
> On Mon, Oct 4, 2021 at 5:46 PM Erik Demaine <[email protected]> wrote:
>> Have folks thought about allowing indexing dictionary views as in the
>> following code, where d is a dict object?
>>
>> d.keys()[0]
>> d.keys()[-1]
>> d.values()[0]
>> d.values()[-1]
>> d.items()[0]
>> d.items()[-1] # item that would be returned by d.popitem()
>
> since dicts were made order-preserving, indexing the keys, items, etc does
> make some sense.
>
>
> > I've also often wanted to get an arbitrary item/key from a dictionary, and
>
> This is indeed one of the use cases identified.
>
>> I found some related discussion in
>> https://mail.python.org/archives/list/[email protected]/thread/QVTGZD6USSC34D4IJG76UPKZRXBBB4MM/
>> but not this exact idea.
>
> That's a pretty different idea but this exact idea has been discussed on this
> list relatively recently. I still like it, but there wan't much general
> support.
>
> I'll leave it exercise for the read to find that thead, but it is there, and
> I suggest you look for it if you want to further pursue this idea.
>
> -CHB
>
>
> --
> Christopher Barker, PhD (Chris)
>
> Python Language Consulting
> - Teaching
> - Scientific Software Development
> - Desktop GUI and Web Development
> - wxPython, numpy, scipy, Cython
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