When I run this script, the task manager shows that when the cache list if full the program uses around 2GB and when popping all elements it goes down to about 20MB.

But, if the surfaces are 255 by 255 instead of 256 by 256 for exemple, it first goes up to 2GB like before, but when emptying the list it stays at 2GB.

import pygame
from pygame import Surface

pygame.init()
pygame.display.set_mode((1280, 720))
clock = pygame.time.Clock()

nb = 10000

running = True
while running:
    for e in pygame.event.get():
        if e.type == pygame.QUIT:
            running = False
        elif e.type == pygame.KEYDOWN:
            if e.key == pygame.K_SPACE and cache:
                for _ in range(nb):
                    cache.pop()
                print("cleaned")
            elif e.key == pygame.K_g:
                cache = [Surface((256, 256)).convert() for _ in range(nb)]
    
    clock.tick(60)

I also tried to use Pympler to get the memory usage by putting this line just after the one that fills up cache: summary.print_(summary.summarize(muppy.get_objects())), it correctly displayed that there were 10000 surfaces but their combined memory usage was only 625KB:

                       types |   # objects |   total size
============================ | =========== | ============
                        code |        3729 |      1.36 MB
                         str |       12611 |      1.35 MB
                        dict |        2315 |    881.16 KB
                        type |         790 |    751.08 KB
      pygame.surface.Surface |       10000 |    625.00 KB
                       tuple |        2504 |    145.08 KB
                        list |         399 |    138.80 KB
                         set |          93 |    119.62 KB
          wrapper_descriptor |        1429 |    100.48 KB
  builtin_function_or_method |        1287 |     90.49 KB
                 abc.ABCMeta |          70 |     86.89 KB
           method_descriptor |        1172 |     82.41 KB
       weakref.ReferenceType |         992 |     77.50 KB
                         int |        1841 |     55.63 KB
                   frozenset |         113 |     46.09 KB

Any ideas as to what could be happening?