node_ListStartEnd.py

import bpy, bmesh, mathutils
from mathutils import Vector, Matrix
from node_s import *
from util import *

class ListFLNode(Node, SverchCustomTreeNode):
    ''' List First and last item of list '''
    bl_idname = 'ListFLNode'
    bl_label = 'List First Last'
    bl_icon = 'OUTLINER_OB_EMPTY'
    
    level = bpy.props.IntProperty(name = 'level_to_count', default=2, min=0, update=updateNode)
    typ = bpy.props.StringProperty(name='typ', default='')
    newsock = bpy.props.BoolProperty(name='newsock', default=False)
    
    def draw_buttons(self, context, layout):
        layout.prop(self, "level", text="level")
        
    def init(self, context):
        self.inputs.new('StringsSocket', "Data", "Data")
        self.outputs.new('StringsSocket',"First","First")
        self.outputs.new('StringsSocket',"Last","Last")

    def update(self):
        if 'Data' in self.inputs and len(self.inputs['Data'].links)>0:
            # адаптивный сокет
            inputsocketname = 'Data'
            outputsocketname = ['First','Last']
            changable_sockets(self, inputsocketname, outputsocketname)
        
        if 'First' in self.outputs and self.outputs['First'].links or \
                'Last' in self.outputs and self.outputs['Last'].links:
            data = SvGetSocketAnyType(self, self.inputs['Data'])
            
            if 'First' in self.outputs and self.outputs['First'].links:
                out = self.count(data, self.level, True)
                SvSetSocketAnyType(self, 'First', out)
            if 'Last' in self.outputs and self.outputs['Last'].links:
                out = self.count(data, self.level, False)
                SvSetSocketAnyType(self, 'Last', out)
            
    def count(self, data, level, First):
        if level:
            out = []
            for obj in data:
                out.append(self.count(obj, level-1, First))
        elif type(data) not in [int, float]:
            if First:
                out = [data[0]]
            else:
                out = [data[-1]]
        return out
            

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

def register():
    bpy.utils.register_class(ListFLNode)   
    
def unregister():
    bpy.utils.unregister_class(ListFLNode)

if __name__ == "__main__":
    register()