def draw(self):
        """ Draws the progress bar if it has changed from it's previous value.  """
        if self.progBar != self.oldprogBar:
            self.oldprogBar = self.progBar
            sys.stdout.write(self.progBar + '\r')
            sys.stdout.flush()      # force updating of screen
 Draws the progress bar if it has changed from it's previous value.  
recipes/Python/578228_Progress_bar_class/recipe-578228.py