shapely.disjoint_subset_union

disjoint_subset_union(a, b, **kwargs)

Merge multiple polygons into one using algorithm optimised for subsets.

Note

‘disjoint_subset_union’ requires at least GEOS 3.12.0.

This is an optimized version of union which assumes inputs can be divided into subsets that do not intersect.

If there is only one such subset, performance can be expected to be worse than union(). As such, it is recommeded to use disjoint_subset_union with GeometryCollections rather than individual geometries.

Added in version 2.1.0.

Parameters:

a, bGeometry or array_like

Geometry or geometries to merge (union).

**kwargs

See NumPy ufunc docs for other keyword arguments.

See also

union

coverage_union

disjoint_subset_union_all

Examples

>>> import shapely
>>> from shapely import Polygon
>>> polygon_1 = Polygon([(0, 0), (0, 1), (1, 1), (1, 0), (0, 0)])
>>> polygon_2 = Polygon([(1, 0), (1, 1), (2, 1), (2, 0), (1, 0)])
>>> shapely.disjoint_subset_union(polygon_1, polygon_2).normalize()
<POLYGON ((0 0, 0 1, 1 1, 2 1, 2 0, 1 0, 0 0))>

Union with None returns same polygon:

>>> shapely.disjoint_subset_union(polygon_1, None).normalize()
<POLYGON ((0 0, 0 1, 1 1, 1 0, 0 0))>