shapely.orient_polygons

orient_polygons(geometry, *, exterior_cw=False, **kwargs)

Enforce a ring orientation on all polygonal elements in the input geometry.

Forces (Multi)Polygons to use a counter-clockwise orientation for their exterior ring, and a clockwise orientation for their interior rings (or the oppposite if exterior_cw=True).

Also processes geometries inside a GeometryCollection in the same way. Other geometries are returned unchanged.

Added in version 2.1.0.

Parameters:

geometryGeometry or array_like

Geometry or geometries to orient consistently.

exterior_cwbool, default False

If True, exterior rings will be clockwise and interior rings will be counter-clockwise.

**kwargs

See NumPy ufunc docs for other keyword arguments.

Examples

A polygon with both shell and hole having clockwise orientation:

>>> from shapely import Polygon, orient_polygons
>>> polygon = Polygon(
...     [(0, 0), (0, 10), (10, 10), (10, 0), (0, 0)],
...     holes=[[(2, 2), (2, 4), (4, 4), (4, 2), (2, 2)]],
... )
>>> polygon
<POLYGON ((0 0, 0 10, 10 10, 10 0, 0 0), (2 2, 2 4, 4 4, 4 2, 2 2))>

By default, the exterior ring is oriented counter-clockwise and the holes clockwise:

>>> orient_polygons(polygon)
<POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0), (2 2, 2 4, 4 4, 4 2, 2 2))>

Asking for the opposite orientation:

>>> orient_polygons(polygon, exterior_cw=True)
<POLYGON ((0 0, 0 10, 10 10, 10 0, 0 0), (2 2, 4 2, 4 4, 2 4, 2 2))>