How to terminate a loop in python with button in GUI

Python Help
1

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 t ?

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(20):
    print("Loop Index = " + str(j))
    time.sleep(0.1)
    j = j+1

# Button START
button_start =  Button(root, text = "START", padx=30, pady=20, command=button_start)
button_start.grid(columnspan=1, row=1,column=0)

# Button STOP
button_stop =  Button(root, text = "STOP", padx=33, pady=20, command=button_stop)
button_stop.grid(row=2,column=0)
2

Try the following. You can have a global variable stop that’s used to control whether the loop stops. When you click the START button, a new thread is created so that the loop runs in a background thread. Note that I renamed your functions because previously, you had functions and Button objects with the same name, which caused problems when I was trying to refer to the function after the Button object of the same name had been created.

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

time.sleep(0.5)

stop = False

def button_stop_command():
  # If the STOP button is pressed then terminate the loop
  global stop
  stop = True

def button_start_command():
  global stop
  stop = False
  j = 1
  while j <= 20 and not stop:
    print("Loop Index = " + str(j))
    time.sleep(0.1)
    j = j+1

def button_starter():
  t = threading.Thread(target=button_start_command)
  t.start()

# Button START
button_start = Button(root, text="START", padx=30, pady=20, command=button_starter)
button_start.grid(columnspan=1, row=1,column=0)

# Button STOP
button_stop = Button(root, text="STOP", padx=33, pady=20, command=button_stop_command)
button_stop.grid(row=2, column=0)

root.mainloop()
1 Like
3

Yes this is working. Thanks for help.