[Tkinter] How to terminate a loop in python with button in GUI

[Joni_Engr]

I am using tkinter. Here is my code. There are two buttons on the GUI. STRAT and STOP. If I press START then a counter up to 30 should be printed on the shell but if I press STOP anytime before the counter reach 30 then the loop should terminate and back to the man loop of GUI. Where should I add thread ?

import time

from tkinter import * 
root = Tk()
root.title("Loop Terminate")

time.sleep(0.5)

# Function button_stop 
def button_stop():
# If the STOP button is pressed then terminate the loop
  i = 1

# Function button_start 
def button_start():
  j = 1
  while j <= int(30):
    print("Loop Index = " + str(j))
    time.sleep(0.5)
    j = j+1

# Button START
button_start =  Button(root, text = "START", padx=53, pady=20, command=button_start)
button_start.grid(columnspan=1, row=1,column=0)

# Button STOP
button_stop =  Button(root, text = "STOP", padx=44, pady=20, command=button_stop)
button_stop.grid(row=2,column=0)