[Python-ideas] Suggestion: Extend integers to include iNaN

[Steve Barnes]

One of the strengths of the IEEE float, (to set against its many 
weaknesses), is the presence of the magic value NaN. Not a Number, or 
NaA, is especially useful in that it is a valid value in any 
mathematical operation, (always returning NaN), or comparison, (always 
returning False). In functional programming this is especially useful as 
it allows the chain to complete after an error while retaining the fact 
that an error occurred, (as we got NaN).

In languages such as C integers can only be used to represent a limited 
range of values in integers and a less limited range of values, (but 
still limited), with a limited accuracy. However, one of Pythons 
strengths is that its integers can represent any whole number value, (up 
to the maximum available memory and in exchange for slow performance 
when numbers get huge). This is accomplished by Python Integers being 
objects rather than a fixed number of bytes.

I think that it should be relatively simple to extend the Python integer 
class to have a NaN flag, possibly by having a bit length of 0, and have 
it follow the same rules for the handling of floating point NaN, i.e. 
any mathematical operation on an iNaN returns an iNaN and any comparison 
with one returns False.

One specific use case that springs to mind would be for Libraries such 
as Pandas to return iNaN for entries that are not numbers in a column 
that it has been told to treat as integers.

We would possibly need a flag to set this behaviour, rather than raising 
an Exception, or at the very least automatically (or provide a method 
to) set LHS integers to iNaN on such an exception.

I thought that I would throw this out to Python Ideas for some 
discussion of whether such a feature is:
  a) Desirable?
  b) Possible, (I am sure that it could be done)?
  c) Likely to get me kicked off of the list?
-- 
Steve (Gadget) Barnes
Any opinions in this message are my personal opinions and do not reflect 
those of my employer.

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