This smells like a bug in the != operator, it seems to fall back to not == which it didn&#39;t used to. More later.....<div><br><br>On Monday, October 8, 2012, Steven D&#39;Aprano  wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
On Mon, Oct 08, 2012 at 09:29:42AM -0700, Guido van Rossum wrote:<br>
<br>
&gt; It&#39;s not about equality. If you ask whether two NaNs are *unequal* the<br>
&gt; answer is *also* False.<br>
<br>
Not so. I think you are conflating NAN equality/inequality with ordering<br>
comparisons. Using Python 3.3:<br>
<br>
py&gt; nan = float(&#39;nan&#39;)<br>
py&gt; nan &gt; 0<br>
False<br>
py&gt; nan &lt; 0<br>
False<br>
py&gt; nan == 0<br>
False<br>
py&gt; nan != 0<br>
True<br>
<br>
but:<br>
<br>
py&gt; nan == nan<br>
False<br>
py&gt; nan != nan<br>
True<br>
<br>
<br>
--<br>
Steven<br>
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</blockquote></div><span></span><br><br>-- <br>--Guido van Rossum (<a href="http://python.org/~guido">python.org/~guido</a>)<br>