Author serhiy.storchaka
Recipients ethan.furman, gvanrossum, josh.r, serhiy.storchaka, steven.daprano, terry.reedy, veky, xtreak
Date 2020-03-11.21:41:19
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Message-id <1583962879.52.0.702341932837.issue35712@roundup.psfhosted.org>
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> How is -1 interpreted?  Does it become a TypeError?

It is interpreted as error. It requires an exception be set. If you return -1 without setting an exception you will usually get a SystemError or crash. Oh, and this may happen during executing other code, so you will search a bug in wrong place.

You cannot change this without breaking the C and Python API in hard way.

> So my thinking is that when the interpreter gets the `NotImplemented` returned by either `if a` or by `if not a` that it would be converted to a `TypeError`

> and the `and` machinery sees it has a `NotImplemented` and raises a `TypeError`.

So you literally want NotImplemented raising a TypeError in boolean context except the "not" operator, and redefine `not a` from

    False if a else True

to

    NotImplemented if a is NotImplemented else False if a else True

You can do this, but this is a different issue, and I doubt that it will solve many problems.
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Date User Action Args
2020-03-11 21:41:19serhiy.storchakasetrecipients: + serhiy.storchaka, gvanrossum, terry.reedy, steven.daprano, ethan.furman, josh.r, veky, xtreak
2020-03-11 21:41:19serhiy.storchakasetmessageid: <1583962879.52.0.702341932837.issue35712@roundup.psfhosted.org>
2020-03-11 21:41:19serhiy.storchakalinkissue35712 messages
2020-03-11 21:41:19serhiy.storchakacreate