I have a dict with string keys:
D = {'a': None, 'b': None}
(the values don't matter for this question) and I want to add a key but
only if it isn't already there. If I do the obvious:
if not 'c' in D:
D['c'] = None
there's a Time Of Check to Time Of Use bug where some other thread could
conceivably insert 'c' into the dict between the check and the insertion.
How do I do a thread-safe insertion if, and only if, the key isn't
already there?
Thanks in advance,
--
Steven D'Aprano
"Ever since I learned about confirmation bias, I've been seeing
it everywhere." -- Jon Ronson
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