Python - How do I continuously repeat a sequence without a While loop and still be able to stop the sequence at any time

Question

I have a Raspberry Pi with the Piface adaptor board. I have made a GUI which controls the LED's on the Piface board. I wrote a small piece of code to make the LED's run up and down continuously, like Knight Riders car, using a While loop. I then wrote another piece of code that created a GUI. In the GUI is a button that starts the LED's running up and down continuously with the While loop piece of code. What I want to do is to have that GUI button start the LED running sequence, and then the same button stop the sequence at any time.

I do understand that the code is sitting/stuck in the While loop. And hence any buttons in the GUI are not going to have an effect.

So is there a better way of doing it? Any pointers would be appreciated.

Thanks in advance.

Answer 1

Another option is to run the LED while loop in a separate thread. Like in the next code. The while loop is stopped by toggling the shared led_switch variable.

"""
blinking LED
"""

import tkinter as tk
import threading
import time

led_switch=False

def start_stop():
    global led_switch
    led_switch=not led_switch
    if led_switch:
        t=threading.Thread(target=LED)
        t.start()

def LED():
    while led_switch:
        print('LED on')
        time.sleep(1)
        print('LED off')
        time.sleep(1)

root=tk.Tk()

button=tk.Button(root,command=lambda: start_stop(),text='start/stop')
button.pack()
tk.mainloop()