Untitled

import tkinter as tk

prozor = tk.Tk()
prozor.geometry("500x300")
prozor.title("Hello world")

labela = tk.Label(prozor,text="Hello world!",width=15,height=5) 
labela.pack()
gumb = tk.Button(prozor,text="Klinkni me",width=20,height=5,command=lambda:labela.config(text="Filip Lilic"))
gumb.pack()
gumbZaIzlaz = tk.Button(prozor,text="Izlaz",width=20,height=5,command=prozor.destroy)
gumbZaIzlaz.pack()
prozor.mainloop()