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Re: Python 3: dict & dict.keys()

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On 07/24/2013 11:01 PM, alex23 wrote:
> On 25/07/2013 4:31 AM, Ethan Furman wrote:
>>    2) Hopefully learn something about when a view is useful.
>
> I haven't seeen this mentioned - forgive me if it's a repeat - but views are constant references to whichever set they
> represent.
>
> Python 2.7:
>
>>>> dd = dict(a=1,b=2,c=3)
>>>> keys = dd.keys()
>>>> 'a' in keys
> True
>>>> dd['d'] = 4
>>>> 'd' in keys
> False
>
> Python 3.3:
>>>> dd = dict(a=1,b=2,c=3)
>>>> keys = dd.keys()
>>>> 'a' in keys
> True
>>>> dd['d'] = 4
>>>> 'd' in keys
> True
>
> If part of my code is only interested in what keys or values are present, it doesn't need to be given a reference to the
> full dictionary, just to whichever view it cares about.

In these cases why is a view better than just using the dict?  Is it a safety so the you don't accidentally modify the dict?

--
~Ethan~

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Re: Python 3: dict & dict.keys() Ethan Furman <ethan@stoneleaf.us> - 2013-07-24 11:31 -0700
  Re: Python 3: dict & dict.keys() alex23 <wuwei23@gmail.com> - 2013-07-25 16:01 +1000
    Re: Python 3: dict & dict.keys() Ethan Furman <ethan@stoneleaf.us> - 2013-07-25 06:47 -0700
  Re: Python 3: dict & dict.keys() Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-07-25 07:04 +0000
    Re: Python 3: dict & dict.keys() Chris Angelico <rosuav@gmail.com> - 2013-07-25 18:02 +1000
    Re: Python 3: dict & dict.keys() Peter Otten <__peter__@web.de> - 2013-07-25 10:13 +0200
    Re: Python 3: dict & dict.keys() Ian Kelly <ian.g.kelly@gmail.com> - 2013-07-25 09:53 -0600
    Re: Python 3: dict & dict.keys() Peter Otten <__peter__@web.de> - 2013-07-25 18:25 +0200

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