[Python-Dev] Add a frozendict builtin type

[Serhiy Storchaka]

01.03.12 11:29, André Malo написав(ла):
> - Caching. My data container objects (say, resultsets from a db or something)
>    usually inherit from list or dict (sometimes also set) and are cached
>    heavily. In order to ensure that they are not modified (accidentially), I
>    have to choices: deepcopy or immutability. deepcopy is so expensive, that
>    it's often cheaper to just leave out the cache. So I use immutability. (oh
>    well, the objects are further restricted with __slots__)

This is the first rational use of frozendict that I see. However, a deep 
copy is still necessary to create the frozendict. For this case, I 
believe, would be better to "freeze" dict inplace and then copy-on-write it.