Safely add a key to a dict only if it does not already exist?
Vito De Tullio
vito.detullio at gmail.com
Sat Jan 19 08:25:27 CET 2013
Steven D'Aprano wrote:
> I wish to add a key to a dict only if it doesn't already exist, but do it
> in a thread-safe manner.
> The naive code is:
> if key not in dict:
> dict[key] = value
> but of course there is a race condition there: it is possible that
> another thread may have added the same key between the check and the
> How can I add a key in a thread-safe manner?
lock = threading.Lock()
if key not in dict:
dict[key] = value
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