import tkinter as tk
import random
def my_func():
 global counter_sec
 label["text"] = str(counter_sec)
 counter_sec+=1
 w = random.randint(25,500)
 h = random.randint(25,500)
 wh = str(w)+"x"+str(h)
 window.geometry(wh)
 window.after(1000, my_func)
counter_sec = 1
window = tk.Tk()
label = tk.Label(text="0")
label.pack()
 
window.after(1000, my_func)
window.mainloop()