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Groups > comp.lang.python > #6518

Re: float("nan") in set or as key

From Wolfgang Rohdewald <wolfgang@rohdewald.de>
Subject Re: float("nan") in set or as key
Date 2011-05-29 10:27 +0200
References <4DE1881C.8000701@mrabarnett.plus.com> <mailman.2207.1306628936.9059.python-list@python.org> <irsarj$2b9$1@reader1.panix.com>
Newsgroups comp.lang.python
Message-ID <mailman.2215.1306657864.9059.python-list@python.org> (permalink)

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On Sonntag 29 Mai 2011, Tim Delaney wrote:
> There's a second part the mystery - sets and dictionaries (and
> I think lists) assume that identify implies equality (hence
> the second result). This was recently discussed on
> python-dev, and the decision was to leave things as-is.

On Sonntag 29 Mai 2011, Grant Edwards wrote:
> Even if they are the same nan, it's still not equal to itself.

if I understand this thread correctly, they are not equal to
itself as specified by IEEE but Python treats them equal in
sets and dictionaries for performance reasons

-- 
Wolfgang

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Thread

Re: float("nan") in set or as key Albert Hopkins <marduk@letterboxes.org> - 2011-05-28 20:28 -0400
  Re: float("nan") in set or as key Erik Max Francis <max@alcyone.com> - 2011-05-28 17:44 -0700
  Re: float("nan") in set or as key Grant Edwards <invalid@invalid.invalid> - 2011-05-29 02:25 +0000
    Re: float("nan") in set or as key Wolfgang Rohdewald <wolfgang@rohdewald.de> - 2011-05-29 10:27 +0200
      Re: float("nan") in set or as key Grant Edwards <invalid@invalid.invalid> - 2011-05-29 14:41 +0000
        Re: float("nan") in set or as key MRAB <python@mrabarnett.plus.com> - 2011-05-29 18:44 +0100
          Re: float("nan") in set or as key Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-29 18:27 +0000
        Re: float("nan") in set or as key Chris Angelico <rosuav@gmail.com> - 2011-05-30 03:50 +1000
        Re: float("nan") in set or as key Christian Heimes <lists@cheimes.de> - 2011-05-29 20:05 +0200
          Re: float("nan") in set or as key Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-29 18:46 +0000
        Re: float("nan") in set or as key Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2011-05-29 20:36 -0700

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