On Sun, May 30, 2010 at 12:07 PM, Lie Ryan <lie.1296@gmail.com> wrote:
In the spirit of collections.OrderedDict and collections.defaultdict, I'd
On 05/30/10 13:27, Benjamin Peterson wrote: 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 -- Imri Goldberg -------------------------------------- http://plnnr.com/ - automatic trip planning http://www.algorithm.co.il/blogs/ -------------------------------------- -- insert signature here ----