[Python-Dev] PEP 468 (original) (raw)

Nathaniel Smith njs at pobox.com
Mon Jun 13 21:33:57 EDT 2016

On Jun 13, 2016 6:16 PM, "MRAB" <python at 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.python.org/pipermail/python-dev/attachments/20160613/76158ad7/attachment.html>

More information about the Python-Dev mailing list