Velocity Reviews (http://www.velocityreviews.com/forums/index.php)
-   Python (http://www.velocityreviews.com/forums/f43-python.html)
-   -   Re: Retrieving an object from a set (http://www.velocityreviews.com/forums/t956941-re-retrieving-an-object-from-a-set.html)

 Ian Kelly 01-25-2013 11:37 PM

Re: Retrieving an object from a set

On Fri, Jan 25, 2013 at 4:30 PM, Ian Kelly <ian.g.kelly@gmail.com> wrote:
> On Fri, Jan 25, 2013 at 4:14 PM, Arnaud Delobelle <arnodel@gmail.com> wrote:
>> Dear Pythoneers,
>>
>> I've got a seemingly simple problem, but for which I cannot find a
>> simple solution.
>>
>> I have a set of objects (say S) containing an object which is equal to
>> a given object (say x). So
>>
>> x in S
>>
>> is true. So there is an object y in S which is equal to x. My
>> problem is how to retrieve y, without going through the whole set.

>
> You could use a dict.
>
>>>> y = (1, 2, 3)
>>>> S = {x: x for x in [y] + range(10000)}
>>>> x = (1, 2, 3)
>>>> x in S

> True
>>>> x is y

> False
>>>> S[x] is y

> True

Or you could use a set intersection:

>>> S = set([y] + list(range(10000)))
>>> S.intersection([x]).pop()

(1, 2, 3)

In my testing, the time needed for this is small and does not seem to
depend on the size of the set.

 All times are GMT. The time now is 05:15 AM.