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

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Peter Otten 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 ...
> 
> But it also sets the value if the key is not found:

yeah, sure, but with a fixed value :)

I mean: if the value is not important, why bother at all trying not to 
override it with an if or a lock or other tecniques? doing

    d['key'] = 'fixed_value'

multiple times in different threads is not a problem in my eyes...

-- 
ZeD

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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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