On Wed, Jan 27, 2010 at 4:55 PM, Steve Howell <showel...@yahoo.com> wrote: > --- On Wed, 1/27/10, John Arbash Meinel <john.arbash.mei...@gmail.com> wrote: > >> From: John Arbash Meinel <john.arbash.mei...@gmail.com> >> Subject: Re: [Python-Dev] patch to make list.pop(0) work in O(1) time >> To: "Steve Howell" <showel...@yahoo.com> >> Cc: "Guido van Rossum" <gu...@python.org>, "Nick Coghlan" >> <ncogh...@gmail.com>, python-dev@python.org >> Date: Wednesday, January 27, 2010, 7:45 AM >> >> > Right now the Python programmer looking to >> aggressively delete elements from the top of a list has to >> consider the tradeoff that the operation takes O(N) time and >> would possibly churn his memory caches with the O(N) memmove >> operation. In some cases, the Python programmer would >> only have himself to blame for not using a deque in the >> first place. But maybe he's a maintenance programmer, >> so it's not his fault, and maybe the code he inherits uses >> lists in a pervasive way that makes it hard to swap in deque >> after the fact. What advice do you give him? >> > >> >> Or he could just set them to None. > > Fair enough, but that's still wasteful of memory, keeping around a bunch of > None elements because you can't inexpensively delete them. I concede that > you can break the dangling references, though, and that's often where large > programs waste a lot of memory, so your point is well taken. >
Why is this thread still going? It seems to me that the case for this change is very weak. Lists, like dicts and tuples, are used *everywhere* and in *vast* quantities. Making them grow by 4 or 8 bytes each for such a corner case can't be an option. I'm sure your new list class has a lot of uses, but it should be an external class. If it stays close in behavior to the lists' behavior, then we could even add a notice in pop()'s documentation that recommends to use your new class in case they want a painless way to replace list usage (to make the life of those poor developers maintaining other people's code easier), maybe even add it in stdlib's "collections" unit. -- Virgil Dupras _______________________________________________ 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
