title: How to get rid of NameError in Python?
body: <p>Hi
  I just executed the following code :</p>
  
  <pre><code>from Tkinter import *
  
  class LabelDemo( Frame ):
     def __init__( self ):
        Frame.__init__( self )   
  
        self.pack( expand = YES, fill = BOTH )
        self.master.title( "Labels" )
  
        self.Label3 = Label( self, bitmap = "warning" )
        self.Label3.pack( side = LEFT )
  
  if __name__ == "__main__":
     LabelDemo().mainloop() 
  </code></pre>
  
  <p>It gives me NameError: name 'LabelDemo' is not defined.</p>
  
  <p>What could be the reason?</p>