New submission from Steven D'Aprano :
The IEEE-754 requirement that NANs are never equal to anything, even to themselves, is a common stumbling block for those new to the consequences of IEEE-754. See for example #47020.
The documentation for math.nan would be a good place to add a note like
"Due to the requirements of the `IEEE-754 standard https://en.wikipedia.org/wiki/IEEE_754`_, math.nan and float('nan') are never equal to any other value, including themselves. Use math.isnan to test for NANs."
https://docs.python.org/3.8/library/math.html#math.nan
----------
assignee: docs@python
components: Documentation
keywords: easy
messages: 415302
nosy: docs@python, steven.daprano
priority: normal
severity: normal
status: open
title: math.nan should note that NANs do not compare equal to anything
type: enhancement
versions: Python 3.10, Python 3.11, Python 3.7, Python 3.8, Python 3.9
_______________________________________
Python tracker
https://bugs.python.org/issue47031
_______________________________________
Charlie Zhao