title: Python tkinter .pack/.pack_forget memory issue
body: <p>I've been teaching myself Python for a few months now and have proceed into learning some GUI techniques.</p>
  
  <p>I wrote this simple script based off a pack_remove example I found within a book.  My script simply displays local and UTC time every second.  Granted the only difference is the hour,  I would still like to redisplay every second.</p>
  
  <p>The script works, yet my RAM is consistently increasing with every time display.  I start out with around 4mb then after 2 hours or so the script uses 25mb.  This makes some sense to me,  but I was curious if there was a way display new times every second, but reduce the memory usage of such a simple clock display.</p>
  
  <p>Or am I using an inefficient technique to re-display data in a GUI at a high frequency?</p>
  
  <p>Here is my code:</p>
  
  <pre><code>from tkinter import *
  import time
  
  class TimeDisplay(Frame):
      def __init__(self,msecs = 1000):
          Frame.__init__(self)
          self.msecs = msecs
          self.pack()
          utc_time = Label(self, text='')
          utc_time.pack()
          cst_time = Label(self, text='')
          cst_time.pack()
          self.utc_time = utc_time
          self.cst_time = cst_time
          self.repeater()
  
      def repeater(self):
          self.utc_time.pack_forget()
          self.cst_time.pack_forget()
          self.utc_time = Label(self, text= 'UTC: ' + time.strftime('%Y/%m/%d %H:%M:%S',time.gmtime()))
          self.utc_time.pack()
          self.utc_time.config(bg='navy',fg='white')
          self.cst_time = Label(self, text= 'CST: ' + time.strftime('%Y/%m/%d %H:%M:%S',time.localtime()))
          self.cst_time.pack()
          self.cst_time.config(bg='navy',fg='white')
          self.after(self.msecs, self.repeater)        
  
  
  if __name__ == '__main__': TimeDisplay(msecs=1000).mainloop()    
  </code></pre>
  
  <p>Thanks in advance</p>