Sets and Membership Tests

[Nick Vatamaniuc]

JK,

You are correct to implement __hash__ and __eq__. The problem is how
you implemented them. Usually your __eq__ method should compare the
necessary attributes of the objects for equality. The __hash__ should
return a 32-bit integer. Your best bet is probably to return a hash of
hashes of your attributes that are used in equality comparison. What
this means is that your attributes used to produce the __hash__ should
also be hashable. This is important yet not immediatly obvious. So you
could for example return hash( (attribute1, attribute2, attribute3) ),
where attribute1, attribute2, attribute3 are all hashable.
 Of course, you provided no code and no error messages (the
'SoFarNoLuck' exception is not descriptive enough ; )

Hope this helps



JKPeck wrote:
> I would like to be able use sets where the set members are objects of a
> class I wrote.
> I want the members to be distinguished by some of the object content,
> but I have not figured out how a set determines whether two (potential)
> elements are identical.  I tried implementing __eq__ and __ne__ and
> __hash__ to make objects with identical content behave as identical for
> set membership, but so far no luck.
>
> I could subclass set if necessary, but I still don't know what I would
> need to override.
> 
> TIA for any advice you can offer.