[Python-Dev] Add a frozendict builtin type (original) (raw)

André Malo nd at perlig.de
Thu Mar 1 15:47:08 CET 2012

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

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