(Shapely.geometry.Polygon to geometry_msgs.PolygonStamped) Shapely polygon representation in RViz

edit

You should check the geometry type before trying to extract the boundaries.

With this you should cover all cases. Let's consider that you object is called multi.

if multi.geom_type == 'MultiPolygon':
        for p in multi:
            if p.geom_type == 'MultiPolygon':
                print("MultiPolygon in MultiPolygon!!!")
                for sp in p:
                    xd,yd = sp.exterior.coords.xy
            elif p.geom_type in ['Point', 'LineString']:
                xd,yd = p.xy
            elif p.geom_type == 'MultiLineString':
                for ea in p:
                    xd,yd = ea.xy
            elif p.geom_type == 'Polygon':
                xd,yd = p.exterior.coords.xy

Then check this link to fill the points list And this one to fill the details of each point

Hope this helps