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

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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

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Thread

subscripting Python 3 dicts/getting the only value in a Python 3 dict Nick Mellor <thebalancepro@gmail.com> - 2016-01-12 08:50 -0800
  RE: subscripting Python 3 dicts/getting the only value in a Python 3 dict Emanuel Barry <vgr255@live.ca> - 2016-01-12 12:00 -0500
  Re: subscripting Python 3 dicts/getting the only value in a Python 3 dict Chris Angelico <rosuav@gmail.com> - 2016-01-13 04:06 +1100
  Re: subscripting Python 3 dicts/getting the only value in a Python 3 dict Terry Reedy <tjreedy@udel.edu> - 2016-01-12 12:12 -0500
  Re: subscripting Python 3 dicts/getting the only value in a Python 3 dict Bernardo Sulzbach <mafagafogigante@gmail.com> - 2016-01-12 15:18 -0200
  Re: subscripting Python 3 dicts/getting the only value in a Python 3 dict Peter Otten <__peter__@web.de> - 2016-01-12 18:32 +0100
  Re: subscripting Python 3 dicts/getting the only value in a Python 3 dict Ian Kelly <ian.g.kelly@gmail.com> - 2016-01-12 10:39 -0700
  Re: subscripting Python 3 dicts/getting the only value in a Python 3 dict Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-01-12 19:47 +0200
    Re: subscripting Python 3 dicts/getting the only value in a Python 3 dict Marko Rauhamaa <marko@pacujo.net> - 2016-01-12 21:42 +0200
      Re: subscripting Python 3 dicts/getting the only value in a Python 3 dict Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-01-12 22:18 +0200
  Re: subscripting Python 3 dicts/getting the only value in a Python 3 dict Peter Otten <__peter__@web.de> - 2016-01-12 19:09 +0100
  Re: subscripting Python 3 dicts/getting the only value in a Python 3 dict Bernardo Sulzbach <mafagafogigante@gmail.com> - 2016-01-12 16:48 -0200
  Re: subscripting Python 3 dicts/getting the only value in a Python 3 dict Peter Otten <__peter__@web.de> - 2016-01-12 19:59 +0100
  Re: subscripting Python 3 dicts/getting the only value in a Python 3 dict Bernardo Sulzbach <mafagafogigante@gmail.com> - 2016-01-12 17:12 -0200
    Re: subscripting Python 3 dicts/getting the only value in a Python 3 dict Steven D'Aprano <steve@pearwood.info> - 2016-01-13 12:29 +1100
      Re: subscripting Python 3 dicts/getting the only value in a Python 3 dict Bernardo Sulzbach <mafagafogigante@gmail.com> - 2016-01-13 13:53 -0200
  Re: subscripting Python 3 dicts/getting the only value in a Python 3 dict Steven D'Aprano <steve@pearwood.info> - 2016-01-13 12:23 +1100
    Re: subscripting Python 3 dicts/getting the only value in a Python 3 dict Grant Edwards <invalid@invalid.invalid> - 2016-01-13 15:58 +0000

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