37 lines
1.3 KiB
Python
37 lines
1.3 KiB
Python
import logging
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import math
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from collections import defaultdict
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from constants import GRID_CELL_SIZE
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log = logging.getLogger("rightmove")
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class PostcodeSpatialIndex:
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"""Grid-based spatial index over arcgis postcodes for nearest-lookup."""
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def __init__(self, lats: list[float], lngs: list[float], postcodes: list[str]):
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self.grid: dict[tuple[int, int], list[tuple[float, float, str]]] = defaultdict(
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list
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)
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for lat, lng, pcd in zip(lats, lngs, postcodes):
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gx = int(math.floor(lng / GRID_CELL_SIZE))
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gy = int(math.floor(lat / GRID_CELL_SIZE))
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self.grid[(gx, gy)].append((lat, lng, pcd))
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log.info(
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"Postcode spatial index: %d cells, %d postcodes", len(self.grid), len(lats)
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)
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def nearest(self, lat: float, lng: float) -> str | None:
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gx = int(math.floor(lng / GRID_CELL_SIZE))
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gy = int(math.floor(lat / GRID_CELL_SIZE))
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best_dist = float("inf")
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best_pcd = None
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for dx in range(-1, 2):
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for dy in range(-1, 2):
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for plat, plng, pcd in self.grid.get((gx + dx, gy + dy), []):
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d = (plat - lat) ** 2 + (plng - lng) ** 2
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if d < best_dist:
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best_dist = d
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best_pcd = pcd
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return best_pcd
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