[issue35712] Make NotImplemented unusable in boolean context

[Steven D'Aprano]

Steven D'Aprano <steve+python at pearwood.info> added the comment:

> the canonical __ne__ delegation to __eq__ for any class should be implemented as something like

I disagree that your code snippet is the canonical way to write __ne__. I'd write it like this:

    def __ne__(self, other):
        return not (self == other)

Or just not write it at all. Python will automatically call __eq__ going back to Python 2.4 (and possibly older).

Delegating to __eq__ directly is the wrong way to do it.

> NotImplemented is a sentinel value that should never be evaluated in a boolean context

I don't see why not. I can't think of any use-cases where I would want to *specifically* use NotImplemented in a boolean context, but I see no good reason why I would want it to fail if one happened to do so.

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nosy: +steven.daprano

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue35712>
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