Shapely Buffering, not working as expected

Question

Why does buffering one of my geometries have an unexpected hole in it?

from shapely import LineString
from geopandas import GeoDataFrame

l = LineString([
  (250,447),
  (319,446),
  (325,387),
  (290,374),
  (259,378),
  (254,385),
  (240,409),
  (244,440),
  (250,447),
])

assert l.is_valid
assert l.is_simple

GeoDataFrame({'geometry': [
  l,
  l.buffer(80),
]}).plot(column='geometry')

• By removing a pair of coordinates, it doesn't have a hole.
• When using Sedona's ST_Buffer this happened in more cases.

Answer 1

from shapely import LineString
from geopandas import GeoDataFrame

l = LineString([
  (250,447),
  (319,446),
  (325,387),
  (290,374),
  (259,378),
  (254,385),
  (240,409),
  (244,440),
  (250,447),
])

l = l.simplify(tolerance=1e-6)

buffered_geometry = l.buffer(80, cap_style=3, join_style=2)

GeoDataFrame({'geometry': [l, buffered_geometry]}).plot(column='geometry')

which is basically what you did.