[Python-ideas] An identity dict

[Raymond Hettinger]

On May 30, 2010, at 7:56 AM, Lie Ryan wrote:

> On 05/31/10 00:23, Benjamin Peterson wrote:
>> Lie Ryan <lie.1296 at ...> writes:
>>> what's wrong with dict[id(key)] = foo?


 . . .

>> 
> 
> it may be useful, but if you can emulate it relatively easily with
> regular dict, why bother with a new type?

I agree that this would be a waste.

Also, I haven't seen much of a discussion of use cases.
It's been possible to make identity dictionaries for a very
long time, yet I can't remember the last time I saw one used.
The Python language makes very few guarantees about
object identity so it is mainly only usable in a few circumstances
where an object is continually referenced by something outside
the identity dict.

I would like to see an identity dict posted an ASPN recipe
to see if anyone actually uses it.


Raymond
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