How to extract interior polygon coordinates using Shapely?

Question

I am new to Shapely (but enthusiastic about it), and recently I\'ve discovered a bit of a road bump.

I have a polygon shapefile that I am reading in via Fiona. This

Answer 1

Interior and exterior rings are structured differently. For any polygon, there is always 1 exterior ring with zero or more interior rings.

So looking at the structure of a geometry, exterior is a LinearRing object, and interiors is a list of zero or more LinearRing objects. Any LinearRing object will have coords, which you can slice to see a list of the coordinates with coords[:].

The following is a function that returns a dict of lists of exterior and interior coordinates:

def extract_poly_coords(geom):
    if geom.type == 'Polygon':
        exterior_coords = geom.exterior.coords[:]
        interior_coords = []
        for interior in geom.interiors:
            interior_coords += interior.coords[:]
    elif geom.type == 'MultiPolygon':
        exterior_coords = []
        interior_coords = []
        for part in geom:
            epc = extract_poly_coords(part)  # Recursive call
            exterior_coords += epc['exterior_coords']
            interior_coords += epc['interior_coords']
    else:
        raise ValueError('Unhandled geometry type: ' + repr(geom.type))
    return {'exterior_coords': exterior_coords,
            'interior_coords': interior_coords}

E.g.:

extract_poly_coords(myShape)