I want to unjumble a constantly jumbling string one letter at a time [closed]

I'm unsure how to make this unscramble to reveal a word, unscrambling one letter at a time from left to right

def jumble():
    letters = string.ascii_letters
    random_letters = ""
    for i in range(5):
        letter = random.choice(letters)
        random_letters += letter
    label.config(text=random_letters)
    window.after(25, jumble)

What I'm trying to do will be usefull in a seperate ciphering program I have, after a certain time (window.after(x, y), this will start unscrambling itself.