iou_profile_intersection_first.ipynb

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   "source": [
    "# Shapely intersection investigation\n",
    "\n",
    "See [Stackoverflow answer](https://stackoverflow.com/a/75821572/3422060)."
   ]
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       "<shapely.geometry.multipolygon.MultiPolygon at 0x7f24482ad820>"
      ]
     },
     "execution_count": 1,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "import shapely.geometry as sg\n",
    "import shapely.affinity\n",
    "\n",
    "a = sg.Polygon([(0, 0), (0, 1), (1, 1), (1, 0), (0, 0)])\n",
    "b = shapely.affinity.translate(a, xoff=2, yoff=2)\n",
    "c = shapely.affinity.translate(a, xoff=0.5, yoff=0.5)\n",
    "\n",
    "sg.MultiPolygon([a, b, c])"
   ]
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   "cell_type": "code",
   "execution_count": 2,
   "id": "ddd405b5-79fa-45d3-81b5-f1d78c7dfadf",
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   "source": [
    "def check_intersects_first(p0: sg.Polygon, p1: sg.Polygon) -> float:\n",
    "    if not p0.intersects(p1):\n",
    "        return 0\n",
    "    return p0.intersection(p1).area / p0.union(p1).area\n",
    "\n",
    "\n",
    "def do_no_check(p0: sg.Polygon, p1: sg.Polygon) -> float:\n",
    "    return p0.intersection(p1).area / p0.union(p1).area"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "id": "1cbf8732-abae-4d3d-a777-11e400791120",
   "metadata": {},
   "outputs": [],
   "source": [
    "assert check_intersects_first(a,b) == do_no_check(a,b) == 0\n",
    "assert check_intersects_first(a,c) == do_no_check(a,c)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "id": "e7ecc377-fc6c-4afe-87af-76815e9bebbb",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "================================================================================\n",
      "Without checking intersects first.\n",
      "--------------------------------------------------------------------------------\n",
      "No intersection\n",
      "1.52 µs ± 39.2 ns per loop (mean ± std. dev. of 7 runs, 1,000,000 loops each)\n",
      "Has Intersection\n",
      "46.1 µs ± 96 ns per loop (mean ± std. dev. of 7 runs, 10,000 loops each)\n",
      "--------------------------------------------------------------------------------\n",
      "\n"
     ]
    }
   ],
   "source": [
    "print(\"=\"*80)\n",
    "print(\"Without checking intersects first.\")\n",
    "print(\"-\"*80)\n",
    "print(\"No intersection\")\n",
    "%timeit check_intersects_first(a,b)\n",
    "\n",
    "print(\"Has Intersection\")\n",
    "%timeit check_intersects_first(a,c)\n",
    "print(\"-\"*80)\n",
    "print()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "id": "a3749687-d094-4af2-819d-e8e75129d175",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "================================================================================\n",
      "Without checking intersects first.\n",
      "--------------------------------------------------------------------------------\n",
      "No intersection\n",
      "23.3 µs ± 1.01 µs per loop (mean ± std. dev. of 7 runs, 10,000 loops each)\n",
      "Has Intersection\n",
      "43.7 µs ± 226 ns per loop (mean ± std. dev. of 7 runs, 10,000 loops each)\n",
      "--------------------------------------------------------------------------------\n"
     ]
    }
   ],
   "source": [
    "print(\"=\"*80)\n",
    "print(\"Without checking intersects first.\")\n",
    "print(\"-\"*80)\n",
    "print(\"No intersection\")\n",
    "%timeit do_no_check(a,b)\n",
    "\n",
    "print(\"Has Intersection\")\n",
    "%timeit do_no_check(a,c)\n",
    "print(\"-\"*80)"
   ]
  },
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   "execution_count": null,
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   "source": []
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  }
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Is your 4th input correct? Should it be "With checking intersects first."?

Yep, the 4th cell print statement should be "With checking intersects first." Thanks @seangrogan!

Yep, the 4th cell print statement should be "With checking intersects first." Thanks @seangrogan!

No worries, thanks friend -- the intersect function you demonstrated helped me solve a problem today!