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From: Vito De Tullio <vito.detullio@gmail.com>
Subject: Re: Safely add a key to a dict only if it does not already exist?
Date: Sat, 19 Jan 2013 08:27:12 +0100
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Xref: csiph.com comp.lang.python:37061

Chris Rebert wrote:

>> How can I add a key in a thread-safe manner?
> I'm not entirely sure, but have you investigated dict.setdefault() ?

but how setdefault makes sense in this context? It's used to set a default 
value when you try to retrieve an element from the dict, not when you try to 
set a new one ...

-- 
ZeD