[Python-Dev] PyObject_RichCompareBool identity shortcut (original) (raw)

Guido van Rossum guido at python.org
Thu Apr 28 05:16:45 CEST 2011

On Wed, Apr 27, 2011 at 11:48 AM, Robert Kern <robert.kern at gmail.com> wrote:

On 4/27/11 12:44 PM, Terry Reedy wrote:

On 4/27/2011 10:53 AM, Guido van Rossum wrote: Maybe we should just call off the odd NaN comparison behavior? Eiffel seems to have survived, though I do not know if it used for numerical work. I wonder how much code would break and what the scipy folks would think. I suspect most of us would oppose changing it on general backwards-compatibility grounds rather than actually liking the current behavior. If the behavior changed with Python floats, we'd have to mull over whether we try to match that behavior with our scalar types (one of which subclasses from float) and our arrays. We would be either incompatible with Python or C, and we'd probably end up choosing Python to diverge from. It would make a mess, honestly. We already have to explain why equality is funky for arrays (arr1 == arr2 is a rich comparison that gives an array, not a bool, so we can't do containment tests for lists of arrays), so NaN is pretty easy to explain afterward.

So does NumPy also follow Python's behavior about ignoring the NaN special-casing when doing array ops?

-- --Guido van Rossum (python.org/~guido)

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