subscripting Python 3 dicts/getting the only value in a Python 3 dict

[Terry Reedy]

On 1/12/2016 11:50 AM, Nick Mellor wrote:
> Hi all,
>
> Seemingly simple problem:
>
> There is a case in my code where I know a dictionary has only one item in it. I want to get the value of that item, whatever the key is.
>
> In Python2 I'd write:
>
>>>> d = {"Wilf's Cafe": 1}
>>>> d.values()[0]
> 1
>
> and that'd be an end to it.
>
> In Python 3:
>
>>>> d = {"Wilf's Cafe": 1}
>>>> d.values()[0]
> Traceback (most recent call last):
>    File "<input>", line 1, in <module>
> TypeError: 'dict_values' object does not support indexing

The intended use of dict views: "Dictionary views can be iterated over 
to yield their respective data, and support membership tests:"

> "Wilf's Cafe"
>>>> d[list(d)[0]]
> 1
>
>>>> for k in d:
> ...     value = d[k]
> ...     break
> ...
>>>> value
> 1
>
>>>> list(d.values())[0]
> 1
>
> None of this feels like the "one, and preferably only one,
 > obvious way to do it" we all strive for. Any other ideas?

Using the values views at intended (as an iterable):

 >>> dv = d.values()
 >>> next(iter(dv))
1

-- 
Terry Jan Reedy