node_KDTreeEdges.py

from node_s import *
from util import *
from mathutils import Vector, kdtree
import bpy

# documentation/blender_python_api_2_70_release/mathutils.kdtree.html


class SvKDTreeEdgesNode(Node, SverchCustomTreeNode):

    bl_idname = 'SvKDTreeEdgesNode'
    bl_label = 'Kdtree Edges'
    bl_icon = 'OUTLINER_OB_EMPTY'

    def draw_buttons(self, context, layout):
        pass

    def init(self, context):
        self.inputs.new('VerticesSocket', 'Verts', 'Verts')
        self.inputs.new('StringsSocket', 'minDistance', 'minDistance')
        self.inputs.new('StringsSocket', 'maxDistance', 'maxDistance')
        self.inputs.new('StringsSocket', 'maxNum', 'maxNum')

        self.outputs.new('StringsSocket', 'Edges', 'Edges')

    def update(self):
        inputs = self.inputs
        outputs = self.outputs

        # if not ('Verts' in inputs and inputs['Verts'].links):
        #     return

        try:
            verts = SvGetSocketAnyType(self, inputs['Verts'])[0]
            mindist = SvGetSocketAnyType(self, inputs['minDistance'])[0][0]
            maxdist = SvGetSocketAnyType(self, inputs['maxDistance'])[0][0]
            maxNum = SvGetSocketAnyType(self, inputs['maxNum'])[0][0]
            # print(mindist, maxdist)
            linked = outputs[0].links
        except (IndexError, KeyError) as e:
            return

        # make kdtree
        # documentation/blender_python_api_2_70_release/mathutils.kdtree.html
        size = len(verts)
        kd = mathutils.kdtree.KDTree(size)

        for i, vtx in enumerate(verts):
            kd.insert(Vector(vtx), i)
        kd.balance()

        # makes edges
        e = []
        maxNum = max(maxNum, 1)
        for i, vtx in enumerate(verts):
            num_edges = 0
            for (co, index, dist) in kd.find_range(vtx, maxdist):
                if i == index or (num_edges > maxNum):
                    continue
                if dist < mindist:
                    continue
                e.append([i, index])
                num_edges += 1

        SvSetSocketAnyType(self, 'Edges', e)

    def update_socket(self, context):
        self.update()


def register():
    bpy.utils.register_class(SvKDTreeEdgesNode)


def unregister():
    bpy.utils.unregister_class(SvKDTreeEdgesNode)

if __name__ == "__main__":
    register()

Wrap the output edges on more time.

How about avoiding duplicate edges?
if e is a set
e.add(tuple(sorted([i,index])))

We could write or own edgSort to keep index in order if the overhead is to large.

It would also be nice to try to prune extra edges at mesh border for non cyclic meshes. That is of course an advanced topic

@ly29, but why tuple? Why not leave lists, that is usual thing. Tuples could be needed on other case maybe.

A set can't have lists as members since they are mutable. Afterwards we can use list(map(list,e)) to change to lists