Calling Polygon.exterior creates noncollectable objects

[Jaakko Salli]

Hi all,

It seems that calling Polygon.exterior generates objects that are not
collectable even by gc.collect(). Attached script reproduces the issue.

Thanks,
  Jaakko




from shapely.geometry import Polygon

import random
import gc

from pprint import pprint

random.seed()
randint = random.randint

gc.enable()
gc.set_debug(gc.DEBUG_SAVEALL)

#
# For some reason, if iterations == 1, no uncollectable
# garbage is generated.
iterations = 2

#
# Let's build some dummy polygons and call their
# exterior property.
for i in range(0, iterations):
    points = []
    x0 = x = float(randint(-100, 100))
    y0 = y = float(randint(-100, 100))
    points.append((x, y))

    for n in range(0, randint(2, 10)):
        x += float(randint(0, 100))
        y += float(randint(0, 100))
        points.append((x, y))

    points.append((x0, y))
    points.append((x0, y0))

    poly = Polygon(points)
    poly.exterior

gc.collect()

pprint(gc.garbage)


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[Sean Gillies]

Jaakko Salli wrote:
>
> Hi all,
>
> It seems that calling Polygon.exterior generates objects that are not
> collectable even by gc.collect(). Attached script reproduces the issue.
>
> Thanks,
>  Jaakko
>

Thanks for the report and script, Jaakko. There's a problem with
circular references here. I have a fix involving weak references, and
just need a day or two to test the cases of interior rings and sub-geoms
of the multipart types. Work around in the meantime is to break the
circular references in your code like:

    ...
    poly = Polygon(points)
    poly.exterior
    ...
    poly._exterior = None
    # end block

Sean

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