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On Jun 13, 2016 6:16 PM, "MRAB" <python@mrabarnett.plus.com> wrote:
\>
\> On 2016-06-14 01:47, Larry Hastings wrote:
\>>
\>> On 06/13/2016 05:05 PM, MRAB wrote:
\>>>
\>>> This could be avoided by expanding the items to include the index of
\>>> the 'previous' and 'next' item, so that they could be handled like a
\>>> doubly-linked list.
\>>>
\>>> The disadvantage would be that it would use more memory.
\>>
\>>
\>> Another, easier technique: don't fill holes. Same disadvantage
\>> (increased memory use), but easier to write and maintain.
\>>
\> When iterating over the dict, you'd need to skip over the holes, so it would be a good idea to compact it a some point, when there are too many holes.

Right -- but if you wait for some ratio of holes to filled space before compacting, you can amortize the cost down, and have a good big-O complexity for both del and iteration simultaneously. Same basic principle as using proportional overallocation when appending to a list, just in reverse.

I believe this is what pypy's implementation actually does.

-n