How to get an item from a simple set?

Bengt Richter bokr at oz.net
Wed Nov 24 18:14:14 CET 2004


On Wed, 24 Nov 2004 09:46:50 -0600, Skip Montanaro <skip at pobox.com> wrote:

>
>    Pete> I have a set that contains one item.  What is the best way of
>    Pete> getting at that item?  Using pop() empties the set.  
>
>Do you want to enumerate all the items in the set?  If so:
>
>    for elt in s:
>        print elt
>
>If you just want to grab one arbitrary (though not random) item from the
>set, try:
>
>    elt = iter(s).next()
>
>Note that repeating this operation will always return the same item:
>
>    >>> s
>    set(['jkl', 'foo', 'abc', 'def', 'ghi'])
>    >>> iter(s).next()
>    'jkl'
>    >>> iter(s).next()
>    'jkl'
>    >>> iter(s).next()
>    'jkl'
>    >>> iter(s).next()
>    'jkl'
>
Lest someone else not realize that the operation you are repeating includes creating
a fresh initialized iterator each time, and you're just doing it as a way to grab one element:

 >>> s = set(['jkl', 'foo', 'abc', 'def', 'ghi'])
 >>> it = iter(s)
 >>> it.next()
 'jkl'
 >>> it.next()
 'foo'
 >>> it.next()
 'abc'
 >>> it.next()
 'def'
 >>> it.next()
 'ghi'
 >>> it.next()
 Traceback (most recent call last):
   File "<stdin>", line 1, in ?
 StopIteration

Regards,
Bengt Richter



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