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Date: Wed, 24 Jul 2013 16:22:11 -0700
From: Ethan Furman <ethan@stoneleaf.us>
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To: Python <python-list@python.org>
Subject: Re: Python 3: dict & dict.keys()
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Xref: csiph.com comp.lang.python:51175

On 07/24/2013 01:34 PM, Prasad, Ramit wrote:
>
> I am still not clear on the advantage of views vs. iterators. What
> makes d.viewkeys() better than d.iterkeys()? Why did they decide
> not to rename d.iterkeys() to d.keys() and instead use d.viewkeys()?
> Is the iteration over a set operation on keys really that common a
> use case?

 From a practical standpoint, iterkeys() is a one-shot deal, while viewkeys() can be iterated over multiple times:

--> d = {1: 'one', 2: 'two', 3: 'three'}

--> di = d.iterkeys()

--> list(di)
[1, 2, 3]

--> list(di)
[]

--> dv = d.viewkeys()

--> list(dv)
[1, 2, 3]

--> list(dv)
[1, 2, 3]

And views are not sets -- they just support a couple set-like operations.

--
~Ethan~