fields.py 文件源码

def get_prep_value(self, value):
        """
        Spatial lookup values are either a parameter that is (or may be
        converted to) a geometry or raster, or a sequence of lookup values
        that begins with a geometry or raster. This routine sets up the
        geometry or raster value properly and preserves any other lookup
        parameters.
        """
        value = super(BaseSpatialField, self).get_prep_value(value)

        # For IsValid lookups, boolean values are allowed.
        if isinstance(value, (Expression, bool)):
            return value
        elif isinstance(value, (tuple, list)):
            obj = value[0]
            seq_value = True
        else:
            obj = value
            seq_value = False

        # When the input is not a geometry or raster, attempt to construct one
        # from the given string input.
        if isinstance(obj, Geometry):
            pass
        else:
            # Check if input is a candidate for conversion to raster or geometry.
            is_candidate = isinstance(obj, (bytes, six.string_types)) or hasattr(obj, '__geo_interface__')
            # Try to convert the input to raster.
            raster = self.get_raster_prep_value(obj, is_candidate)

            if raster:
                obj = raster
            elif is_candidate:
                try:
                    obj = Geometry(obj)
                except (GeometryException, GDALException):
                    raise ValueError("Couldn't create spatial object from lookup value '%s'." % obj)
            else:
                raise ValueError('Cannot use object with type %s for a spatial lookup parameter.' % type(obj).__name__)

        # Assigning the SRID value.
        obj.srid = self.get_srid(obj)

        if seq_value:
            lookup_val = [obj]
            lookup_val.extend(value[1:])
            return tuple(lookup_val)
        else:
            return obj