On Wednesday 29 February 2012 20:17:05 Raymond Hettinger wrote: > On Feb 27, 2012, at 10:53 AM, Victor Stinner wrote: > > A frozendict type is a common request from users and there are various > > implementations. > > ISTM, this request is never from someone who has a use case. > Instead, it almost always comes from "completers", people > who see that we have a frozenset type and think the core devs > missed the ObviousThingToDo(tm). Frozendicts are trivial to > implement, so that is why there are various implementations > (i.e. the implementations are more fun to write than they are to use). > > The frozenset type covers a niche case that is nice-to-have but > *rarely* used. Many experienced Python users simply forget > that we have a frozenset type. We don't get bug reports or > feature requests about the type. When I do Python consulting > work, I never see it in a client's codebase. It does occasionally > get discussed in questions on StackOverflow but rarely gets > offered as an answer (typically on variants of the "how do you > make a set-of-sets" question). If Google's codesearch were still > alive, we could add another datapoint showing how infrequently > this type is used.
Here are my real-world use cases. Not for security, but for safety and performance reasons (I've built by own RODict and ROList modeled after dictproxy): - Global, but immutable containers, e.g. as class members - 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__) I agree, these are not general purpose issues, but they are not *rare*, I'd think. nd _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
