# Tk_chr_per_sec.py

# Tk_chr_per_sec.py

from tkinter import *
import random
theList = ['a', 'b', 'c', 'd', 'e']
windows = Tk()
windows.geometry("40x40")
a = StringVar()
a.set(' ')
label = Label(windows, textvariable=a, width=1)
label.pack()

while 1:
    random.shuffle(theList)
    for i in range(6):
        windows.after(1000)
        a.set((theList+['-'])[i].upper())
        windows.update()
windows.mainloop()