Issue 21823: Catch turtle.Terminator exceptions in turtledemo (original) (raw)

When a turtle update operation cannot finish because the underlying canvas has been cleared (when the STOP button is pushed), turtle.Terminator is raised. When turtledemo runs the main function of a demo, it catches any Termininator raised before main returns.

However, special demos leave an event loop running after main returns. If the demo is free running, as with clock and minimal_hanoi, clicking STOP causes such exceptions. (This is not be a problem with paint as updates only happen in response to mouse events on the canvas and complete before a user could move the mouse to the STOP button.)

This is the clock trackback, with common file prefix removed: \tkinter_init.py", line 1487, in call return self.func(*args) \tkinter_init.py", line 532, in callit func(args) \turtledemo\clock.py", line 116, in tick second_hand.setheading(6sekunde) \turtle.py", line 1935, in setheading self._rotate(angle) \turtle.py", line 3277, in _rotate self._update() \turtle.py", line 2659, in _update self._update_data() \turtle.py", line 2645, in _update_data self.screen._incrementudc() \turtle.py", line 1291, in _incrementudc raise Terminator

The hanoi traceback starts differently: \tkinter_init.py", line 1487, in call return self.func(*args) \turtle.py", line 686, in eventfun fun() \turtledemo\minimal_hanoi.py", line 53, in play hanoi(6, t1, t2, t3) ...<5 recursive calls deleted> \turtledemo\minimal_hanoi.py", line 36, in push to.push(from_.pop()) \turtledemo\minimal_hanoi.py", line 36, in push d.setx(self.x) \turtle.py", line 1807, in setx self._goto(Vec2D(x, self._position[1])) \turtle.py", line 3178, in _goto <last 3 lines as above>

These exceptions and tracebacks do not stop the master demo window, but are printed to the console (python -m turtledemo) or Idle Shell (open in editor, run). They are ugly, might unnecessarily alarm a naive user, or falsely teach that tracebacks are to be ignored.

In the patch to clock.tick, I put try: at the top, to be safe, although just before the update of the second hand might be good enough.