Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #37069

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

Show all headers | View raw

On 01/19/2013 02:35 AM, Mitya Sirenef wrote:
> 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
>
>

Er, that makes no sense.. just setdefault to desired value. -m



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

Back to comp.lang.python | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

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

csiph-web