turtle regression in 3.5

[gotyaoi]

BPO	26571
Nosy	@ethanfurman, @serhiy-storchaka, @gotyaoi, @furkanonder, @williamnavaraj
PRs	bpo-26571: fix Turtle Terminator Exception #19465 bpo-26571-Class variable _RUNNING update at the __init__ end #30332 bpo-26571: Reinit class variable _RUNNING #30355

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/serhiy-storchaka'
closed_at = None
created_at = <Date 2016-03-16.04:59:15.427>
labels = ['type-bug', 'library', '3.9', '3.10', '3.11']
title = 'turtle regression in 3.5'
updated_at = <Date 2022-01-06.15:52:29.164>
user = 'https://github.com/gotyaoi'

bugs.python.org fields:

activity = <Date 2022-01-06.15:52:29.164>
actor = 'williamnavaraj'
assignee = 'serhiy.storchaka'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2016-03-16.04:59:15.427>
creator = 'Ellison Marks'
dependencies = []
files = []
hgrepos = []
issue_num = 26571
keywords = ['patch']
message_count = 6.0
messages = ['261840', '263589', '273190', '279343', '366212', '409866']
nosy_count = 7.0
nosy_names = ['ethan.furman', 'python-dev', 'serhiy.storchaka', 'Ellison Marks', 'Robert Harder', 'furkanonder', 'williamnavaraj']
pr_nums = ['19465', '30332', '30355']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue26571'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']

Linked PRs

• [3.15] gh-70758: Fix creating a turtle screen after closing one (GH-30355) #155449
• [3.14] gh-70758: Fix creating a turtle screen after closing one (GH-30355) #155450
• [3.13] gh-70758: Fix creating a turtle screen after closing one (GH-30355) #155451

[gotyaoi]

I noticed some odd behaviour when running some turtle code I wrote using python 3.5. A simplified example:

>>> from turtle import Turtle
>>> t = Turtle()
>>> t.getscreen().bye() # or manually close the turtle window
>>> t2 = Turtle()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib64/python3.5/turtle.py", line 3816, in __init__
    visible=visible)
  File "/usr/lib64/python3.5/turtle.py", line 2557, in __init__
    self._update()
  File "/usr/lib64/python3.5/turtle.py", line 2660, in _update
    self._update_data()
  File "/usr/lib64/python3.5/turtle.py", line 2646, in _update_data
    self.screen._incrementudc()
  File "/usr/lib64/python3.5/turtle.py", line 1292, in _incrementudc
    raise Terminator
turtle.Terminator
>>>

This code works under 3.4, opening a new turtle window the second time Turtle() is called. Under 3.5, a blank white window opens.

This seems to be related to https://hg.python.org/cpython/rev/1628484c9408, as the only point that raises Terminator is guarded by a check for `if not TurtleScreen._RUNNING:`

[gotyaoi]

Just as an update, I've been working around this by manually setting TurtleScreen._RUNNING to True before calling Turtle() again, which produces the desired behaviour in both 3.4 and 3.5. Haven't noticed any bad effects so far.

[ethanfurman]

Serhiy, is this a quick fix you can get in?

[RobertHarder]

Thanks for pointing out the workaround. Was driving me crazy. Possible fix is to add TurtleScreen._RUNNING = True ~line 967 in turtle.py, in TurtleScreen.__init__ function.

[furkanonder]

PR has been sent.

[williamnavaraj]

Hi all,
Sorry. I seem to have stepped on someone's toes or no one likes turtle any more (as this is active since 2016). As you can see, I am new here and still getting a feel for these procedures. I was preparing a Jupyter notebook for my students. I planned some exercises with turtle at start before we jump into real robots. I noticed this annoying Terminator error, digged deeper into the code to find about the _RUNNING class variable. The PR from Furkan suggest to remove the Raise Terminator. May be we could amend that and I will close my PR, if you prefer.

Thanks,