title: Making a countdown timer with Python and Tkinter?
body: <p>I want to set a label in Tkinter using my countdown timer function. Right now all it does is set the lable to "10" once 10 is reached and I don't really understand why. Also, even if I have the timer print to a terminal instead the "Time's up!" bit never prints.</p>
  
  <pre><code>import time
  import tkinter as tk
  
  class App():
      def __init__(self):
          self.root = tk.Tk()
          self.label = tk.Label(text="null")
          self.label.pack()
          self.countdown()
          self.root.mainloop()
  
      # Define a timer.
      def countdown(self):
          p = 10.00
          t = time.time()
          n = 0
          # Loop while the number of seconds is less than the integer defined in "p"
          while n - t &lt; p: 
              n = time.time()
              if n == t + p:
                  self.label.configure(text="Time's up!")
              else:
                  self.label.configure(text=round(n - t))
  
  app=App()
  </code></pre>