# -*- coding: utf-8 -*-
import tkinter as tk
root = tk.Tk()
root.title("tk5.py")
root.geometry("100x100")
#####################################
def hello():
    lb.config(text = 'Hello!')
    
btn = tk.Button(root, text = "Hello", \
borderwidth = 10, bg = '#0000ff', \
fg = 'yellow', command = hello)

lb = tk.Label(root, text = 'A Label', fg = 'darkgreen')

btn.pack()
lb.pack()
#####################################
root.mainloop()