New submission from Terry J. Reedy:
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(6*sekunde)
\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.
--
assignee: terry.reedy
messages: 221215
nosy: terry.reedy
priority: normal
severity: normal
stage: needs patch
status: open
title: Catch turtle.Terminator exceptions in turtledemo
type: behavior
versions: Python 2.7, Python 3.4, Python 3.5
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http://bugs.python.org/issue21823
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