from tkinter import *
from tkinter.ttk import *

def my_button_behavior():
    '''executes when the 'hello' button is clicked'''
    button_text.set('You clicked me!')

def main():
    window = Tk()   # create the main program window
    
    global button_text
    button_text = StringVar()
    button_text.set('Click me')
    
    button = Button(window, textvariable=button_text, command=my_button_behavior)
    button.grid(row=0, column=0)
    button.configure(padding=50)
    
    window.mainloop() # enter the GUI main loop
    

main()