On Thursday 01 March 2012 15:17:35 Serhiy Storchaka wrote:
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.
In my case it's actually a half one. The data mostly comes from memcache ;) I'm populating the object and then I'm done with it. People wanting to modify it, need to copy it, yes. OTOH usually a shallow copy is enough (here). Funnily my ROList actually provides a "sorted" method instead of "sort" in order to create a sorted copy of the list. nd