Python 3: dict & dict.keys()

Ethan Furman ethan at stoneleaf.us
Thu Jul 25 01:22:11 CEST 2013


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~



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