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Re: Safely add a key to a dict only if it does not already exist?

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Date Sat, 19 Jan 2013 02:35:12 -0500
From Mitya Sirenef <msirenef@lightbird.net>
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Subject Re: Safely add a key to a dict only if it does not already exist?
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On 01/19/2013 02:27 AM, Vito De Tullio wrote:
> 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 ...
>

I guess setdefault with a sentinel default value, then set to your
new value if d[k] is sentinel?

  - mitya


-- 
Lark's Tongue Guide to Python: http://lightbird.net/larks/

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Thread

Safely add a key to a dict only if it does not already exist? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-19 04:07 +0000
  Re: Safely add a key to a dict only if it does not already exist? Chris Rebert <clp2@rebertia.com> - 2013-01-18 20:15 -0800
    Re: Safely add a key to a dict only if it does not already exist? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-19 10:31 +0000
  Re: Safely add a key to a dict only if it does not already exist? Lie Ryan <lie.1296@gmail.com> - 2013-01-19 16:00 +1100
  Re: Safely add a key to a dict only if it does not already exist? Vito De Tullio <vito.detullio@gmail.com> - 2013-01-19 08:25 +0100
  Re: Safely add a key to a dict only if it does not already exist? Vito De Tullio <vito.detullio@gmail.com> - 2013-01-19 08:27 +0100
  Re: Safely add a key to a dict only if it does not already exist? Mitya Sirenef <msirenef@lightbird.net> - 2013-01-19 02:35 -0500
  Re: Safely add a key to a dict only if it does not already exist? Peter Otten <__peter__@web.de> - 2013-01-19 09:02 +0100
  Re: Safely add a key to a dict only if it does not already exist? Vito De Tullio <vito.detullio@gmail.com> - 2013-01-19 09:16 +0100
  Re: Safely add a key to a dict only if it does not already exist? Mitya Sirenef <msirenef@lightbird.net> - 2013-01-19 03:18 -0500
  Re: Safely add a key to a dict only if it does not already exist? Vito De Tullio <vito.detullio@gmail.com> - 2013-01-19 09:19 +0100
  Re: Safely add a key to a dict only if it does not already exist? Chris Angelico <rosuav@gmail.com> - 2013-01-19 19:23 +1100
  Re: Safely add a key to a dict only if it does not already exist? Roy Smith <roy@panix.com> - 2013-01-19 08:04 -0500

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