[Python-Dev] Retrieve an arbitrary element from asetwithoutremoving it

[Alexander Belopolsky]

On Mon, Nov 9, 2009 at 10:09 AM, Daniel Stutzbach
<daniel at stutzbachenterprises.com> wrote:
> On Mon, Nov 9, 2009 at 2:42 AM, "Martin v. Löwis" <martin at v.loewis.de>
> wrote:
>>
>> Interesting. Something goes wrong, it seems: if items get removed over
>> and over again, I think the set should shrink (not sure whether it
>> actually does). Then, I think you should end up with an amortized O(1)
>> for selecting an element (assuming that the underlying hashes don't
>> collide).
>
> I'm not sure if Python's implementation shrinks or not,

It does not:

>>> s = set(range(100000))
>>> from sys import getsizeof
>>> getsizeof(s)
4194536
>>> while s: x = s.pop()
...
>>> getsizeof(s)
4194536
>>> s.clear()
>>> getsizeof(s)
232