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[Python-Dev] PEP for new dictionary implementation
Mark Shannonmark at hotpy.org
Fri Feb 17 18:52:23 CET 2012
On 17 February 2012 at 17:42 Jim Jewett <jimjjewett at gmail.com> wrote:> On Fri, Feb 17, 2012 at 1:50 AM, "Martin v. Löwis" <martin at v.loewis.de>wrote:> >>> Good idea. However, how do you track per-dict how large the> >>> table is?>> [Or, rather, what is the highest index needed to store any values> that are actually set for this instance.]>> > To determine whether it needs to grow the array, it needs to find out> > how large the array is, no? So: how do you do that?>> Ah, now I understand; you do need a single ssize_t either on the dict> or at the head of the values array to indicate how many slots it has> actually allocated. It *may* also be worthwhile to add a second> ssize_t to indicate how many are currently in use, for faster results> in case of len. But the dict is guaranteed to have at least one free> slot, so that extra index will never make the allocation larger than> the current code.The dict already has a field indicating how many items are in use,the ma_used field.Cheers,Mark.
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