from tkinter import *
from tkinter.ttk import *

from time import strftime

root=Tk()
root.title('clock')

def time():
    string=strftime('%H:%M:%S ')
    label.config(text=string)
    label.after(1000,time)
label= Label(root, font=('ds-digital',80), background="black",foreground='yellow') #install ds-digital font just searching on  google
label.pack(anchor='center')

time()

mainloop()