[Python-ideas] Identity dicts and sets

[Terry Reedy]

On 1/2/2013 9:01 AM, Serhiy Storchaka wrote:
> I propose to add new standard collection types: IdentityDict and
> IdentitySet. They are almost same as ordinal dict and set, but uses

What do you mean by ordinal dict, as opposed to plain dict.

> identity check instead of equality check (and id() or hash(id()) as a

By default, equality check is identity check.

> hash). They will be useful for pickling, for implementing __sizeof__()
> for compound types, and for other graph algorithms.

I don't know anything about pickling or __sizeof__, by if one uses 
user-defined classes for nodes and edges, equality is identity, so I 
don't see what would be gained.

The disadvantage of multiple minor variations on dict is confusion among 
users as to specific properties and use cases.

-- 
Terry Jan Reedy