Guido van Rossum writes:
Sounds good. (But now maybe we also need to come clean with the exceptions for NaNs compared as part of container comparisons?)
For a second I thought you meant IEEE 754 Exceptions. Whew! How about:
""" For reasons of efficiency, Python allows comparisons of containers to shortcut element comparisons. These shortcuts mean that it is possible that comparison of two containers may return True, even if they contain NaNs. For details, see the language reference. """
Longer than I think it deserves, but maybe somebody has a better idea?
Footnotes:  Sorry about that, but details don't really belong in a *Python* tutorial. Maybe this should be "see the implementation notes"?