[Python-ideas] unify usage of mutable and immutable objects
mertz at gnosis.cx
Tue Feb 28 18:14:33 EST 2017
On Tue, Feb 28, 2017 at 2:57 PM, 语言破碎处 <mlet_it_bew at 126.com> 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
> 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.
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