# Countdown using Tkinter from Tkinter import *import timeimport tkMessageBoxclass App: def __init__(self,master):  frame = Frame(master)  frame.pack()  self.entryWidget = Entry(frame)  self.entryWidget["width"] = 15  self.entryWidget.pack(side=LEFT)  self.hi_there = Button(frame,text="Start",command=self.start)  self.hi_there.pack(side=LEFT)  self.button = Button(frame,text="QUIT",fg="red",command=frame.quit)  self.button.pack(side=LEFT) def start(self):  text = self.entryWidget.get().strip()  if text != "":   num = int(text)   self.countDown(num) def countDown(self,seconds):  lbl1.config(bg='yellow')  lbl1.config(height=3, font=('times',20,'bold'))  for k in range(seconds, 0, -1):   lbl1["text"] = k   root.update()   time.sleep(1)  lbl1.config(bg='red')  lbl1.config(fg='white')  lbl1["text"] = "Time up!"  tkMessageBox.showinfo("Time up!","Time up!") def GetSource():  get_window = Tkinter.Toplevel(root)  get_window.title('Source File?')  Tkinter.Entry(get_window, width=30,      textvariable=source).pack()  Tkinter.Button(get_window, text="Change",      command=lambda: update_specs()).pack()root = Tk()root.title("Countdown")lbl1 = Label()lbl1.pack(fill=BOTH, expand=1)app = App(root)root.mainloop()