On Sun, May 30, 2010 at 12:07 PM, Lie Ryan
<lie.1296@gmail.com> wrote:
On 05/30/10 13:27, Benjamin Peterson wrote:
> In the spirit of collections.OrderedDict and collections.defaultdict, I'd like
> to propose collections.identitydict. It would function just like a normal
> dictionary, but ignore hash values and comparison operators and merely lookup
> keys based on the key's id().
>
> This dict is very useful for keep track of objects that should not be compared
> by normal comparison methods. For example, I would use an identitydict to hold
> weak references that would otherwise fallback to their referant object's hash.
My 2 bits:
1. I implemented and used such a dict a few years ago, as part of a graph/tree algorithm. While I don't have access to the source anymore, I mainly wanted to bring up an example for the usage of such a data structure. Still, I haven't needed it since, so take from it what you will.
what's wrong with dict[id(key)] = foo?
2. Mostly that you want other operators to work as well. In your example, "key in dic" will return False, as __contains__ is the standard implementation.
Cheers,
Imri