title: tkinter.messagebox.showinfo doesn't always work
body: <p>I have just started working with Python's <code>tkinter</code> GUI tool. In my code I create an simple GUI with one button and I want to show the user a <code>messagebox</code> if they click on the button.</p>
  
  <p>Currently, I use the <code>tkinter.messagebox.showinfo</code> method for it. I code on a Windows 7 computer using IDLE. If I run the code from IDLE everything works fine, but if I try to run it standalone in the Python 3 interpreter it doesn't work any more. Instead it logs this error to the console:</p>
  
  <pre><code>AttributeError:'module' object has no attribute 'messagebox'
  </code></pre>
  
  <p>Do you have any tips for me? My code is:</p>
  
  <pre><code>import tkinter
  
  class simpleapp_tk(tkinter.Tk):
      def __init__(self,parent):
          tkinter.Tk.__init__(self,parent)
          self.parent = parent
          self.temp = False
          self.initialize()
  
      def initialize(self):
          self.geometry()
          self.geometry("500x250")
          self.bt = tkinter.Button(self,text="Bla",command=self.click)
          self.bt.place(x=5,y=5)
      def click(self):
          tkinter.messagebox.showinfo("blab","bla")
  
  if __name__ == "__main__":
      app = simpleapp_tk(None)
      app.title('my application')
      app.mainloop()
  </code></pre>