On Sun, Dec 29, 2019 at 08:22:49AM -0500, David Mertz wrote: > Signalling NaN's are a pain because I'd want: > > is_nan(snan) == True > > But statistics.median([1, 2, snan], on_nan='ignore') to raise an exception.
So you want to skip quiet NANs and raise on signalling NANs? I'd like to understand the use-case here. I guess it is "signalling NANs are an error, quiet NANs are missing data". Am I right? How are the signalling NANs going to get into your data? As far as I know, there are no operations in Python which will naturally return a signalling NAN, you have to inject them into the data yourself: (1) The float() constructor doesn't accept "snan"; no arithmetic operations or math module libraries return signalling NANs, so the only way to create a sNAN is using the struct module. But that's not guaranteed to succeed: as per the link I gave earlier https://mail.python.org/archives/list/python-...@python.org/thread/35NECLGFIVAHWTIPAYDBJOJJX3FSY233/ that's platform-dependent. So there's no platform-independent way to get a float sNAN, or guarantee that it will work the way you want. (2) The Decimal constructor does accept "snan", and it it platform- independent. But as far as I can tell there's no way to get a sNAN out as the result of any Decimal operation. Invalid operations will either return a quiet NAN, or raise. Either way, float or Decimal, the only way to get a sNAN in your data is to put it there yourself. Why not just raise at the point of inserting the ~~landmine~~ sNAN instead? Alternately, could you use None or object()? With the exception of mode, the statistics functions will fail with TypeError. -- Steven _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/36Q6O3DBMD5L45PHDBVRZ4ONI6WUW5VV/ Code of Conduct: http://python.org/psf/codeofconduct/
