title: Turtle does not run more than once in jupyter notebook
body: <p>I am trying to run some turtle code in jupyter notebook. When I run the code once, the code runs fine. However, if I run the code again, Python Turtle Graphics freezes and closes (aka python turtle graphics is not responding) and the jupyter notebook's kernel crashes</p>
  
  <p>I have tried to switch notebooks, reinstalling jupyter and restarting the kernel, but none of them worked.</p>
  
  <p>Here is the turtle code:</p>
  
  <pre><code>import turtle
  pen = turtle.Pen()
  window = turtle.Screen()
  pen.color("light blue")
  pen.shape("turtle")
  pen.forward(100)
  
  window.exitonclick()
  </code></pre>
  
  <p>Here is the error message when I run the code for the second time. The note book is saved at C:\Users\fligh\OneDrive\Jupyter Notebooks\ and the file name is "Principles 2 Playground":</p>
  
  <pre><code>&lt;ipython-input-2-79042881c88e&gt; in &lt;module&gt;
        1 import turtle
  ----&gt; 2 pen = turtle.Pen()
        3 window = turtle.Screen()
        4 pen.color("light blue")
        5 pen.shape("turtle")
  
  c:\users\fligh\appdata\local\programs\python\python37-32\lib\turtle.py in __init__(self, shape, undobuffersize, visible)
     3814                            shape=shape,
     3815                            undobuffersize=undobuffersize,
  -&gt; 3816                            visible=visible)
     3817 
     3818 Pen = Turtle
  
  c:\users\fligh\appdata\local\programs\python\python37-32\lib\turtle.py in __init__(self, canvas, shape, undobuffersize, visible)
     2555         self._undobuffersize = undobuffersize
     2556         self.undobuffer = Tbuffer(undobuffersize)
  -&gt; 2557         self._update()
     2558 
     2559     def reset(self):
  
  c:\users\fligh\appdata\local\programs\python\python37-32\lib\turtle.py in _update(self)
     2658             return
     2659         elif screen._tracing == 1:
  -&gt; 2660             self._update_data()
     2661             self._drawturtle()
     2662             screen._update()                  # TurtleScreenBase
  
  c:\users\fligh\appdata\local\programs\python\python37-32\lib\turtle.py in _update_data(self)
     2644 
     2645     def _update_data(self):
  -&gt; 2646         self.screen._incrementudc()
     2647         if self.screen._updatecounter != 0:
     2648             return
  
  c:\users\fligh\appdata\local\programs\python\python37-32\lib\turtle.py in _incrementudc(self)
     1290         if not TurtleScreen._RUNNING:
     1291             TurtleScreen._RUNNING = True
  -&gt; 1292             raise Terminator
     1293         if self._tracing &gt; 0:
     1294             self._updatecounter += 1
  
  Terminator:
  </code></pre>
  
  <p>Can someone help me?
  Thanks</p>