On 19/01/13 15:15, Chris Rebert wrote:
On Friday, January 18, 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
store.
How can I add a key in a thread-safe manner?
I'm not entirely sure, but have you investigated dict.setdefault() ?
dict.setdefault() was not atomic on older python version, they were made
atomic in Python 2.7.3 and Python 3.2.3.
See bug13521 in the issue tracker http://bugs.python.org/issue13521
PS: The bug tracker seems down at the moment, so pulled this from
Google's cache:
https://webcache.googleusercontent.com/search?q=cache:59PO_F-VEfwJ:bugs.python.org/issue13521+&cd=1&hl=en&ct=clnk&client=ubuntu
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