title: Switching between frames in tkinter menu
body: <p>I've used Tkinter to create a GUI with different menu options (a similar example is produced below). Each menu has different commands, which when clicked create a new frame. Now what is happening is if I switch to a different command, the new frame stacks below the current frame instead of replacing the old one.</p>
  
  <p>I want to know what is the best way to move forward.</p>
  
  <pre><code>import Tkinter as tkinter
  root = tkinter.Tk()
  root.minsize(400,300)
  welcome = tkinter.Frame(root).grid()
  label = tkinter.Label(welcome, text="Welcome to my program").grid(row=0, column=3)
  button = tkinter.Button(welcome,text="Exit",command=root.destroy).grid(row=3, column=1)
  def newFrame():
  newFrame = tkinter.Frame(root).grid()
  newFrame_name = tkinter.Label(newFrame, text="This is another frame").grid()
  menu = tkinter.Menu(root)
  root.config(menu=menu)
  main_menu = tkinter.Menu(menu)
  menu.add_cascade(label="Main Menu", menu= main_menu)
  main_menu.add_command(label="New Frame", command=newFrame)
  main_menu.add_command(label="Another Frame", command=newFrame)
  #menu.add_command(label="Exit", command=root.destroy, menu= filemenu)
  root.mainloop()
  </code></pre>
  
  <p>Now if I switch between New Frame and Another Frame, the windows stack up, but I want one window to replace the other.</p>
  
  <p>Any ideas? Thanks.</p>