[issue27754] Changing the meaning of bool.__invert__

[Raymond Hettinger]

Raymond Hettinger added the comment:

>>> ... it would be nice if ~ acted as negation on bools (~False being
>>> True and ~True being false) instead of mapping them to -1 and -2 
>>> as it currently does.

I'm strongly against this proposal for several reasons.

1. One way to do it.  We don't need a second way to spell "not x".  As a Python teacher, I will find it harder to explain the language with this change (sometimes ~ sometimes means bitwise-not and sometimes it means "not").

2. We were supposed to learn from our mistake using "%" for string formatting which causes problems because the operator precedence was the same as multiplication and division and inappropriate for formatting.   In the case, the precedence for the bitwise-and/or/not is very different from boolean-and/or/not (the former occur before comparisons and the latter occur after comparisons).

3. Not all Liskov violations matter, but it is not uncommon to rely on True and False being interchangeable with 1 and 0.  I suspect this change will break some existing code in a way that is hard to find and may not be covered by existing unit tests.

4. If we care at all about Python 3 adoption, we will stop introducing hundreds of little breakages and changes in meaning that add almost no value but do increase the difficultly (and cost) of moving to Python 3.  Guido has referred to this as "death by a thousand cuts".

So please put me down with R. David Murray as recommending that this proposal to be deemed "officially dropped".

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nosy: +rhettinger

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue27754>
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