Depending on how you imported tkinter you may have to put end in quotations Try:
self.listNodes.delete(0,'end')
you can also use:
self.listNodes.delete(0,tk.END)
Replace:
self.listNodes.delete(0,END)
with:
self.listNodes.delete('0','end')
END is a variable of tkinter module, which suggests either a wildcard(from tkinter import *) import or from tkinter import END was supposed to be used.
END
from tkinter import *
from tkinter import END
You can use this is you imported tkinter as:
import tkinter as tkself.listnodes.delete(0, tk.END)
Or you can do:
from tkinter import *self.listnodes.delete(0, END)