How to break a loop in this case?

[bowlofred]

Unless you create some sort of multi-threaded app (which is not easy), there's no way to stop a function from the outside. The outside program is just waiting for the function to return.

Some options:
That marketloop() function is doing a lot of repetitive things. A loop would be good for it. If you had the data in a nice map, you could loop over them, and then check for the keypress (and exit) if you see it.

files = {
    "offers": "offers.PNG"
    "search": "search.PNG"
    "settings": "settings.PNG"
}

def marketloop():
    for region, filename in files.each():
        data = pg.locateCenterOnScreen(filename, region=(0,0,1919,1079), grayscale=False, confidence=0.80)
        time.sleep(0.5)
        pg.click(data.x, data.y)
        time.sleep(0.5)
        if check_keypress() == pressed: #however you do this...
            return # Exits the function immediately.