[Python-Dev] Getting values stored inside sets
alexander.belopolsky at gmail.com
Fri Apr 3 19:16:24 CEST 2009
I just want to add a link to a 2.5 year old discussion on this issue:
<http://bugs.python.org/issue1507011>. In that discussion I disagreed
with Martin and argued that "interning is a set
operation and it is unfortunate that set API does not support it directly."
On Fri, Apr 3, 2009 at 12:43 PM, "Martin v. Löwis" <martin at v.loewis.de> wrote:
>> I've stumbled upon an oddity using sets. It's trivial to test if a
>> value is in the set, but it appears to be impossible to retrieve a
>> stored value, other than by iterating over the whole set.
> Of course it is. That's why it is called a set: it's an unordered
> collection of objects, keyed by nothing.
> If you have a set of elements, and you check "'foo' in s", then
> you should be able just to use the string 'foo' itself for whatever
> you want to do with it - you have essentially created a set of
> strings. If you think that 'foo' and Element('foo') are different
> things, you should not implement __eq__ in a way that they are
> considered equal.
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