IDLE: ignore completion ValueError for list.remove()

[rhettinger]

BPO	45197
Nosy	@rhettinger, @terryjreedy

^{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/terryjreedy'
closed_at = None
created_at = <Date 2021-09-14.15:33:16.373>
labels = ['expert-IDLE', 'type-bug', '3.9']
title = 'IDLE should suppress ValueError for list.remove()'
updated_at = <Date 2021-09-15.03:00:13.699>
user = 'https://github.com/rhettinger'

bugs.python.org fields:

activity = <Date 2021-09-15.03:00:13.699>
actor = 'terry.reedy'
assignee = 'terry.reedy'
closed = False
closed_date = None
closer = None
components = ['IDLE']
creation = <Date 2021-09-14.15:33:16.373>
creator = 'rhettinger'
dependencies = []
files = []
hgrepos = []
issue_num = 45197
keywords = []
message_count = 2.0
messages = ['401782', '401807']
nosy_count = 2.0
nosy_names = ['rhettinger', 'terry.reedy']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue45197'
versions = ['Python 3.9']

Linked PRs

• gh-89360: Fix ValueError in IDLE MultiCall event_delete #152738
• [3.15] gh-89360: Fix ValueError in IDLE MultiCall event_delete (GH-152738) #152802
• [3.14] gh-89360: Fix ValueError in IDLE MultiCall event_delete (GH-152738) #152803
• [3.13] gh-89360: Fix ValueError in IDLE MultiCall event_delete (GH-152738) #152804

[rhettinger]

I got this today running a stock Python 3.9.6 for macOS downloaded from python.org.

-------------------------------------------------------------

Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/tkinter/__init__.py", line 1892, in __call__
    return self.func(*args)
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/idlelib/multicall.py", line 176, in handler
    r = l[i](event)
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/idlelib/autocomplete_w.py", line 350, in keypress_event
    self.hide_window()
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/idlelib/autocomplete_w.py", line 463, in hide_window
    self.widget.event_delete(HIDE_VIRTUAL_EVENT_NAME, seq)
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/idlelib/multicall.py", line 392, in event_delete
    triplets.remove(triplet)
ValueError: list.remove(x): x not in list

[terryjreedy]

The offending function is

        def event_delete(self, virtual, *sequences):
            if virtual not in self.__eventinfo:
                return
            func, triplets = self.__eventinfo[virtual]
            for seq in sequences:
                triplet = _parse_sequence(seq)
                if triplet is None:
                    #print("Tkinter event_delete: %s" % seq, file=sys.__stderr__)
                    widget.event_delete(self, virtual, seq)
                else:
                    if func is not None:
                        self.__binders[triplet[1]].unbind(triplet, func)
                    triplets.remove(triplet)

The triplets collection is part of *virtual* whereas each triplet is derived from a member of sequences.
The discrepancy seems to be extremely rare. I will catch the exception until such time as I see a plausible, reproducible, and testable reason.