# documentación de Django - 1.10.7

# Código fuente para django.contrib.gis.geos.polygon

    from ctypes import byref, c_uint

    from django.contrib.gis.geos import prototypes as capi
    from django.contrib.gis.geos.geometry import GEOSGeometry
    from django.contrib.gis.geos.libgeos import GEOM_PTR, get_pointer_arr
    from django.contrib.gis.geos.linestring import LinearRing
    from django.utils import six
    from django.utils.six.moves import range

    class Polygon(GEOSGeometry):
        _minlength = 1

        def __init__(self, *args, **kwargs):
            """
            Initializes on an exterior ring and a sequence of holes (both
            instances may be either LinearRing instances, or a tuple/list
            that may be constructed into a LinearRing).

            Examples of initialization, where shell, hole1, and hole2 are
            valid LinearRing geometries:
            >>> from django.contrib.gis.geos import LinearRing, Polygon
            >>> shell = hole1 = hole2 = LinearRing()
            >>> poly = Polygon(shell, hole1, hole2)
            >>> poly = Polygon(shell, (hole1, hole2))

            >>> # Example where a tuple parameters are used:
            >>> poly = Polygon(((0, 0), (0, 10), (10, 10), (0, 10), (0, 0)),
            ...                ((4, 4), (4, 6), (6, 6), (6, 4), (4, 4)))
            """
            if not args:
                super(Polygon, self).__init__(self._create_polygon(0, None), **kwargs)
                return

            # Getting the ext_ring and init_holes parameters from the argument list
            ext_ring = args[0]
            init_holes = args[1:]
            n_holes = len(init_holes)

            # If initialized as Polygon(shell, (LinearRing, LinearRing)) [for backward-compatibility]
            if n_holes == 1 and isinstance(init_holes[0], (tuple, list)):
                if len(init_holes[0]) == 0:
                    init_holes = ()
                    n_holes = 0
                elif isinstance(init_holes[0][0], LinearRing):
                    init_holes = init_holes[0]
                    n_holes = len(init_holes)

            polygon = self._create_polygon(n_holes + 1, (ext_ring,) + init_holes)
            super(Polygon, self).__init__(polygon, **kwargs)

        def __iter__(self):
            "Iterates over each ring in the polygon."
            for i in range(len(self)):
                yield self[i]

        def __len__(self):
            "Returns the number of rings in this Polygon."
            return self.num_interior_rings + 1

        @classmethod
        def from_bbox(cls, bbox):
            "Constructs a Polygon from a bounding box (4-tuple)."
            x0, y0, x1, y1 = bbox
            for z in bbox:
                if not isinstance(z, six.integer_types + (float,)):
                    return GEOSGeometry('POLYGON((%s %s, %s %s, %s %s, %s %s, %s %s))' %
                                        (x0, y0, x0, y1, x1, y1, x1, y0, x0, y0))
            return Polygon(((x0, y0), (x0, y1), (x1, y1), (x1, y0), (x0, y0)))

        # ### These routines are needed for list-like operation w/ListMixin ###
        def _create_polygon(self, length, items):
            # Instantiate LinearRing objects if necessary, but don't clone them yet
            # _construct_ring will throw a TypeError if a parameter isn't a valid ring
            # If we cloned the pointers here, we wouldn't be able to clean up
            # in case of error.
            if not length:
                return capi.create_empty_polygon()

            rings = []
            for r in items:
                if isinstance(r, GEOM_PTR):
                    rings.append(r)
                else:
                    rings.append(self._construct_ring(r))

            shell = self._clone(rings.pop(0))

            n_holes = length - 1
            if n_holes:
                holes = get_pointer_arr(n_holes)
                for i, r in enumerate(rings):
                    holes[i] = self._clone(r)
                    holes_param = byref(holes)
            else:
                holes_param = None

            return capi.create_polygon(shell, holes_param, c_uint(n_holes))

        def _clone(self, g):
            if isinstance(g, GEOM_PTR):
                return capi.geom_clone(g)
            else:
                return capi.geom_clone(g.ptr)

        def _construct_ring(self, param, msg=(
                'Parameter must be a sequence of LinearRings or objects that can initialize to LinearRings')):
            "Helper routine for trying to construct a ring from the given parameter."
            if isinstance(param, LinearRing):
                return param
            try:
                ring = LinearRing(param)
                return ring
            except TypeError:
                raise TypeError(msg)

        def _set_list(self, length, items):
            # Getting the current pointer, replacing with the newly constructed
            # geometry, and destroying the old geometry.
            prev_ptr = self.ptr
            srid = self.srid
            self.ptr = self._create_polygon(length, items)
            if srid:
                self.srid = srid
            capi.destroy_geom(prev_ptr)

        def _get_single_internal(self, index):
            """
            Returns the ring at the specified index.  The first index, 0, will
            always return the exterior ring.  Indices > 0 will return the
            interior ring at the given index (e.g., poly[1] and poly[2] would
            return the first and second interior ring, respectively).

            CAREFUL: Internal/External are not the same as Interior/Exterior!
            _get_single_internal returns a pointer from the existing geometries for use
            internally by the object's methods.  _get_single_external returns a clone
            of the same geometry for use by external code.
            """
            if index == 0:
                return capi.get_extring(self.ptr)
            else:
                # Getting the interior ring, have to subtract 1 from the index.
                return capi.get_intring(self.ptr, index - 1)

        def _get_single_external(self, index):
            return GEOSGeometry(capi.geom_clone(self._get_single_internal(index)), srid=self.srid)

        _set_single = GEOSGeometry._set_single_rebuild
        _assign_extended_slice = GEOSGeometry._assign_extended_slice_rebuild

        # #### Polygon Properties ####
        @property
        def num_interior_rings(self):
            "Returns the number of interior rings."
            # Getting the number of rings
            return capi.get_nrings(self.ptr)

        def _get_ext_ring(self):
            "Gets the exterior ring of the Polygon."
            return self[0]

        def _set_ext_ring(self, ring):
            "Sets the exterior ring of the Polygon."
            self[0] = ring

        # Properties for the exterior ring/shell.
        exterior_ring = property(_get_ext_ring, _set_ext_ring)
        shell = exterior_ring

        @property
        def tuple(self):
            "Gets the tuple for each ring in this Polygon."
            return tuple(self[i].tuple for i in range(len(self)))
        coords = tuple

        @property
        def kml(self):
            "Returns the KML representation of this Polygon."
            inner_kml = ''.join(
                "<innerBoundaryIs>%s</innerBoundaryIs>" % self[i + 1].kml
                for i in range(self.num_interior_rings)
            )
            return "<Polygon><outerBoundaryIs>%s</outerBoundaryIs>%s</Polygon>" % (self[0].kml, inner_kml)