title: Create a line using a list of coordinates in python GUI
body: <p>I've been trying to create a graph using a create_line and a list of (x,y) points. </p>
  
  <pre><code>import Tkinter
  Screen = [a list of screen coordinates]
  World = []
  for x,y in screen:
      World.append(somefunctiontochange(x,y))
      if len(World) &gt;= 2:
          Canvas.create_line(World)
  </code></pre>
  
  <p>The line doesn't show in my canvas though, and no error was given. Any help?</p>