How to break a loop in this case?

[Blainexi]

I got this to work, but when I press s to stop the script, it will keep running the marketloop() function till end before stopping. My question is that how do I make the function stop instantly too? I tried adding break in stop buffing function but returned an expected 'break' outside loop error.

import pyautogui as pg
import time
import keyboard
import random
import win32api, win32con
import threading
from pynput.mouse import Button, Controller
from pynput.keyboard import Listener, KeyCode

start_stop_key = KeyCode(char='s')
exit_key = KeyCode(char='q')

def marketloop():
      #this has code that clicks through lots of things


class BuffItems(threading.Thread):
    def __init__(self):
        super(BuffItems, self).__init__()
        self.running = False
        self.program_running = True

    def start_buffing(self):
        self.running = True

    def stop_buffing(self):
        self.running = False
        

    def exit(self):
        self.stop_buffing()
        self.program_running = False

    def run(self):
        while self.program_running:
            while self.running:
                marketloop()


                
buff_thread = BuffItems()
buff_thread.start()
                

def on_press(key):
    if key == start_stop_key:
        if buff_thread.running:
            buff_thread.stop_buffing()
        else:
            buff_thread.start_buffing()
    elif key == exit_key:
        buff_thread.exit()
        listener.stop()

with Listener(on_press=on_press) as listener:
    listener.join()