[Python-Dev] py2.7: dictobject not properly resizing

[Armin Rigo]

Hi Antoine,

On Sat, Mar 30, 2013 at 10:37 PM, Antoine Pitrou <solipsis at pitrou.net> wrote:
> On Sat, 30 Mar 2013 17:31:26 -0400
> Micha Gorelick <mynameisfiber at gmail.com> wrote:
>> I was taking a look at dictobject.c and realized that the logic
>> controlling whether a resizedict will occur in
>> dict_set_item_by_hash_or_entry disallows for the shrinking of a
>> dictionary.

It doesn't disallow shrinking.  If you take a dictionary of size 1000,
remove of its elements, and continue to use it (write and delete more
items) for long enough, then eventually it is shrinked.  It just takes
a while because it needs to fill 2/3 of the slots of the big table
with "deleted" markers before it happens.

Python 3.3.0b1 (default:07ddf5ecaafa, Aug 12 2012, 17:47:28)
[GCC 3.4.6 (Gentoo 3.4.6-r2, ssp-3.4.6-1.0, pie-8.7.10)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> d = {i:i for i in range(1000)}
>>> sys.getsizeof(d)
24624
>>> for i in range(1000): del d[i]
...
>>> sys.getsizeof(d)
24624
>>> for j in range(1001, 2000):
...    d[j] = 0; del d[j]
...
>>> sys.getsizeof(d)
144
>>>


A bientôt,

Armin.