I'm trying to construct a KDtree for finding 'K nearest neighbour' I've created a class called 'Point' which holds attributes: pointID, lat (latitude) and Lon (longitude). the input for the build_index is an array 'points' contains all instances of points.

in the code below I'm trying to construct the KDtree but I'm having issues with trying to retrieve just the lat and Lon of each Point to sort, but I understand just using 'points' will not work as it is a an array with just the class instances.

thanks for the help in advance!

class KDTreeNN(NearestNeigh):

   def build_index(self, points: [Point]):
       depth = 0
       n = len(points)
       if n <0:
           return None
       axis = depth % 2
       sorted_points = sorted(points, key = lambda point: point[axis])
       depth   1
       return {
           'point' : sorted_points[int(n/2)],
           'left' : self.build_index(sorted_points[:int(n/2)]),
           'right' : self.build_index(sorted_points[int(n/2)   1:])
       }

CodePudding user response：

point[axis] is not working because point does not support such bracket notation.

There are several solutions:

1. Define Point as a named tuple:

   Instead of defining Point as something like:

   class Point:
       def __init__(self, pointID, lat, lon):
           self.pointID = pointID
           self.lat = lat
           self.lon = lon
   

   ...define it as a named tuple. Make sure to make lon and lat its first two members:

   Point = namedtuple("Point", "lat,lon,pointID")
   

   Also ensure that were create Point instances, you put the arguments in the right order.

   With that change it will work. This requires that you treat Point instances as immutable.

2. Access the attribute (lon or lat) depending on a string variable:

   axis = ("lon", "lat")[depth % 2]
   sorted_points = sorted(points, key = lambda point: getattr(point, axis))