On 2012-10-26 17:23, Steven D'Aprano wrote:
On Fri, 26 Oct 2012 04:00:03 -0400, Terry Reedy wrote:
On 10/25/2012 10:19 PM, MRAB wrote:
In summary, .index() looks for an item which is equal to its argument,
but it's a feature of NaN (as defined by the standard) that it doesn't
equal NaN, therefore .index() will never find it.
Except that is *does* find the particular nan object that is in the
collection. So nan in collection and list.index(nan) look for the nan by
identity, not equality.
So it does. I made the same mistake as MRAB, thank you for the correction.
[snip]
Yes, I forgot that Python checks for identity before checking for
equality:
>>> [float("nan")].index(float("nan"))
Traceback (most recent call last):
File "<pyshell#0>", line 1, in <module>
[float("nan")].index(float("nan"))
ValueError: nan is not in list
>>> nan = float("nan")
>>> [nan].index(nan)
0
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