Как связать listbox и button?

>>> from tkinter import*
>>> import math
>>> def Summa (x,y,z):
 return((math.sin(x)+math.fabs(-z))/(2*y+2*math.sqrt(pow(x,2)-4*x*y)))
 
>>> k=Summa(x=6,y=1,z=10)
>>> def listbox_event():
 if listbox.get():
  listbox['k']=listbox.get()
 else:
  pass
 
>>> root=Tk()
>>> listbox=Listbox(root,height=5,width=10,selectmode=EXTENDED)
>>> Button=Button(width=5,height=7,text='Summa',command=listbox_event)
>>> Button.pack()
>>> listbox.pack()
>>> root.mainloop()

import tkinter
 
 
def add_listbox(event, data, listbox):
    listbox.insert(tkinter.END, data.get())
 
 
root = tkinter.Tk()
 
box = tkinter.Listbox(root, selectmode=tkinter.EXTENDED)
box.pack()
 
text = tkinter.Entry()
text.pack()
 
but = tkinter.Button(text='add')
but.pack()
but.bind('<ButtonRelease-1>', lambda event: add_listbox(event, text, box))
 
root.mainloop()

import tkinter
 
def add_listbox():
    box.insert(tkinter.END, text.get())
 
 
root = tkinter.Tk()
 
box = tkinter.Listbox(root, selectmode=tkinter.EXTENDED)
box.pack()
 
text = tkinter.Entry()
text.pack()
 
but = tkinter.Button(text='add', command=add_listbox)
but.pack()
 
root.mainloop()