from tkinter import * # Import tkinter
    
class PackManagerDemo:
    def __init__(self):
        window = Tk() # Create a window
        window.title("Pack Manager Demo 1") # Set title
        
        Label(window, text = "Blue", bg = "blue").pack()
        Label(window, text = "Red", bg = "red").pack(
            fill = BOTH, expand = 1)
        Label(window, text = "Green", bg = "green").pack(
            fill = BOTH)
        
        window.mainloop() # Create an event loop

PackManagerDemo() # Create GUI