import tkinter as tk

class Application(tk.Frame):
    def __init__(self, master=None):
        tk.Frame.__init__(self, master)
        self.pack()
        self.createWidgets()

    def createWidgets(self):
        self.hi_there = tk.Button(self)
        self.hi_there["text"] = "Hello_World\n(click_me)",
        self.hi_there["command"] = self.say_hi
        self.hi_there.pack({"side": "top"})

        self.QUIT = tk.Button(self, text = "QUIT", fg = "red", command = root.destroy)
        self.QUIT.pack({"side": "bottom"})

    def say_hi(self):
        print("hi there, everyone!")

root = tk.Tk()
app = Application(master=root)
app.mainloop()