SIngleton from defaults

Newsgroups	comp.lang.python
Date	2014-01-22 08:07 -0800
Message-ID	<26ff768d-349c-48cd-a46f-25343807e18a@googlegroups.com> (permalink)
Subject	SIngleton from __defaults__
From	Asaf Las <roegltd@gmail.com>

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Hi 

Inspired by "Modifying the default argument of function"
https://groups.google.com/forum/#!topic/comp.lang.python/1xtFE6uScaI

is it possible to create singleton using construct below : 

def singleton_provider(x = [None]):
    if singleton_provider.__defaults__[0][0] == None:
        singleton_provider.__defaults__[0][0] = SomeClass()
    return singleton_provider.__defaults__[0][0]

and question - how to make it work in multithreaded app
when multiple threads are racing to create it first?

Thanks 

Asaf

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SIngleton from __defaults__ Asaf Las <roegltd@gmail.com> - 2014-01-22 08:07 -0800
  Re: SIngleton from __defaults__ Chris Angelico <rosuav@gmail.com> - 2014-01-23 03:18 +1100
    Re: SIngleton from __defaults__ Asaf Las <roegltd@gmail.com> - 2014-01-22 08:37 -0800
      Re: SIngleton from __defaults__ 88888 Dihedral <dihedral88888@gmail.com> - 2014-01-22 09:23 -0800
      Re: SIngleton from __defaults__ Ned Batchelder <ned@nedbatchelder.com> - 2014-01-22 14:18 -0500
        Re: SIngleton from __defaults__ Asaf Las <roegltd@gmail.com> - 2014-01-22 11:52 -0800
      Re: SIngleton from __defaults__ Johannes Schneider <johannes.schneider@galileo-press.de> - 2014-01-23 14:36 +0100
      Re: SIngleton from __defaults__ Dave Angel <davea@davea.name> - 2014-01-23 11:56 -0500
      Re: SIngleton from __defaults__ Terry Reedy <tjreedy@udel.edu> - 2014-01-23 19:10 -0500
      Re: SIngleton from __defaults__ Johannes Schneider <johannes.schneider@galileo-press.de> - 2014-01-24 09:20 +0100
    Re: SIngleton from __defaults__ Asaf Las <roegltd@gmail.com> - 2014-01-22 13:10 -0800
    Re: SIngleton from __defaults__ Asaf Las <roegltd@gmail.com> - 2014-01-22 14:34 -0800

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