Re: Retrieving an object from a set

Discussion in 'Python' started by MRAB, Jan 25, 2013.

  1. MRAB

    MRAB Guest

    On 2013-01-25 23:14, Arnaud Delobelle 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.
    > Here is a simple illustration with tuples (my actual scenario is not
    > with tuples but with a custom class):
    >
    >>>> y = (1, 2, 3) # This is the 'hidden object'
    >>>> S = set([y] + range(10000))
    >>>> x = (1, 2, 3)
    >>>> x in S

    > True
    >>>> x is y

    > False
    >

    You could first limit the search to only those which it could be:

    S & set([y])

    A search would be:

    >>> f = [m for m in S & set([y]) if m is y][0]
    >>> f is y

    True
    MRAB, Jan 25, 2013
    #1
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