def __init__(self, geom_input, srs=None):

        self._ptr = c_void_p(None) # Initially NULL
        str_instance = isinstance(geom_input, basestring)

        # If HEX, unpack input to to a binary buffer.
        if str_instance and hex_regex.match(geom_input):
            geom_input = buffer(a2b_hex(geom_input.upper()))
            str_instance = False

        # Constructing the geometry, 
        if str_instance:
            # Checking if unicode
            if isinstance(geom_input, unicode):
                # Encoding to ASCII, WKT or HEX doesn't need any more.
                geom_input = geom_input.encode('ascii')

            wkt_m = wkt_regex.match(geom_input)
            json_m = json_regex.match(geom_input)
            if wkt_m:
                if wkt_m.group('type').upper() == 'LINEARRING':
                    # OGR_G_CreateFromWkt doesn't work with LINEARRING WKT.
                    #  See http://trac.osgeo.org/gdal/ticket/1992.
                    g = create_geom(OGRGeomType(wkt_m.group('type')).num)
                    import_wkt(g, byref(c_char_p(geom_input)))
                else:
                    g = from_wkt(byref(c_char_p(geom_input)), None, byref(c_void_p()))
            elif json_m:
                if GEOJSON:
                    g = from_json(geom_input)
                else:
                    raise NotImplementedError('GeoJSON input only supported on GDAL 1.5+.')
            else:
                # Seeing if the input is a valid short-hand string
                # (e.g., 'Point', 'POLYGON').
                ogr_t = OGRGeomType(geom_input)
                g = create_geom(OGRGeomType(geom_input).num)
        elif isinstance(geom_input, buffer):
            # WKB was passed in
            g = from_wkb(str(geom_input), None, byref(c_void_p()), len(geom_input))
        elif isinstance(geom_input, OGRGeomType):
            # OGRGeomType was passed in, an empty geometry will be created.
            g = create_geom(geom_input.num)
        elif isinstance(geom_input, c_void_p):
            # OGR pointer (c_void_p) was the input.
            g = geom_input
        else:
            raise OGRException('Invalid input type for OGR Geometry construction: %s' % type(geom_input))

        # Now checking the Geometry pointer before finishing initialization
        # by setting the pointer for the object.
        if not g:
            raise OGRException('Cannot create OGR Geometry from input: %s' % str(geom_input))
        self._ptr = g

        # Assigning the SpatialReference object to the geometry, if valid.
        if bool(srs): self.srs = srs

        # Setting the class depending upon the OGR Geometry Type
        self.__class__ = GEO_CLASSES[self.geom_type.num]
Initializes Geometry on either WKT or an OGR pointer as input.
dataset/ETHPy150Open dcramer/django-compositepks/django/contrib/gis/gdal/geometries.py/OGRGeometry.__init__