import tkinter as tk
import time

root = tk.Tk()


def skan():
    label.config(text="Ale wcisnales!!")
    time.sleep(4)
    label.config(text="I po wcisnieciu:(")


label = tk.Label(root, text="Ciskaj!")
label.pack()
but = tk.Button(root, text="KLIK!", command=skan)
but.pack()

root.mainloop()