# shapely.coverage_union_all#

coverage_union_all(geometries, axis=None, **kwargs)#

Returns the union of multiple polygons of a geometry collection. This is an optimized version of union which assumes the polygons to be non-overlapping.

This function ignores None values when other Geometry elements are present. If all elements of the given axis are None, an empty GeometryCollection is returned (before GEOS 3.12 this was an empty MultiPolygon).

Parameters:
geometriesarray_like
axisint, optional

Axis along which the operation is performed. The default (None) performs the operation over all axes, returning a scalar value. Axis may be negative, in which case it counts from the last to the first axis.

**kwargs

See NumPy ufunc docs for other keyword arguments.

Examples

```>>> from shapely import normalize, 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)])
>>> normalize(coverage_union_all([polygon_1, polygon_2]))
<POLYGON ((0 0, 0 1, 1 1, 2 1, 2 0, 1 0, 0 0))>
>>> normalize(coverage_union_all([polygon_1, None]))
<POLYGON ((0 0, 0 1, 1 1, 1 0, 0 0))>
>>> normalize(coverage_union_all([None, None]))
<GEOMETRYCOLLECTION EMPTY>
```