On Tuesday, February 28, 2017 at 6:48:42 PM UTC-5, 语言破碎处 wrote: > > > A hypothetical frozenset.pop() is also necessarily O(N). It needs to > copy N-1 elements into the new (smaller) frozenset object. So this isn't > an argument. > Pop tuple/frozenset(standard one) gain no benefit. # O(n) > It is a different story for balanced tree. # O(log n) > > > Sounds like `collections.deque` might be what you want (for concurrency, > not for immutability). But a local copy will require, by definition, a > *copy* operation either way. > My intent is to unify "SET" interface, not for to using deque. > I want something that is SET can use anywhere regardless mutable or > not. > And the idiom SHOULD work for other type. > > WHY set.add / list.sort return None? > if return self, someone may think it don't modify the orignal object. > so, mutable object will have different methods. > Such differences are good UNLESS we want to ignore it explictly. > We need a uniform way to make a interface suitable for both cases. > > collections.abc.Set is the uniform interface suitable for mutable and immutable sets:
https://docs.python.org/3/library/collections.abc.html It contains: __contains__, __iter__, __len__ __le__, __lt__, __eq__, __ne__, __gt__, __ge__, __and__, __or__, __sub__, __xor__, and isdisjoint Is there something missing? I don't think add should be there. I think if you want to start mutating a (possibly immutable) set, you should convert it to set (pay the linear cost up-front) and then start mutating it. > > At 2017-03-01 07:14:33, "David Mertz" <me...@gnosis.cx <javascript:>> > wrote: > > On Tue, Feb 28, 2017 at 2:57 PM, 语言破碎处 <mlet_...@126.com <javascript:>> > wrote: > >> 1) coverting to set or list is O(n) in time >> > > A hypothetical frozenset.pop() is also necessarily O(N). It needs to copy > N-1 elements into the new (smaller) frozenset object. So this isn't an > argument. > > >> 2) if I have to keep the old copy, >> standard set solution will be O(n) both in time and space! >> > > Again, nothing gained here. Same applies to frozenset.pop() (assuming it > returns both the item popped and a reduced set). If you just want > "something from frozenset" without creating a new almost-copy frozenset, > that is spelled `next(iter(fs))`. > > >> working examples: >> 1) priority queue: >> insert and pop occur >> 2) share immutable data to difference subroutines: >> each one can modify local copy safely and concurrency. >> > > Sounds like `collections.deque` might be what you want (for concurrency, > not for immutability). But a local copy will require, by definition, a > *copy* operation either way. > > > -- > Keeping medicines from the bloodstreams of the sick; food > from the bellies of the hungry; books from the hands of the > uneducated; technology from the underdeveloped; and putting > advocates of freedom in prisons. Intellectual property is > to the 21st century what the slave trade was to the 16th. > > > > >
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