Martin Panter added the comment: Funny, I ran into this one or two days ago, when refactoring some code that used the bitwise exclusive-or operator, since there is no boolean exclusive or:
-if (x == a) ^ (y != b): ... +aa = x == a +bb = y == b +if aa ^ not bb: ... It is fairly clear what I wanted to do above, but with “is not” you would have to avoid ambiguity: >>> "spam" is not "ham" # Using “is not” operator True >>> "spam" is (not "ham") # Two distinct operators False I think it would be too complicated to make unary “not” bind more tightly than “and” in some cases but not in others. How would you handle these cases? a + not b and c a ** not b ** c a is not not b The way I see it, there is no equivalent problem with the other unary operators: arithmetic (+, -), bitwise (~), and “await”. Await has higher priority than all other binary operators, so no problem there. The other three are equal with the highest priority binary operator, exponentiation (**): >>> 2 ** -1 ** 2 # Evaluated right to left 0.5 >>> 2 ** (-1) ** 2 # Negation first 2 >>> (2 ** -1) ** 2 # Left-hand exponentiation first 0.25 BTW, in the operator precedence table <https://docs.python.org/dev/reference/expressions.html#operator-precedence>, I think exponentiation should be in the same priority group as the arithmetic and bitwise unary operations. At the moment it says exponentiation has higher priority, but has a footnote saying this is reversed on the right-hand side of an exponentiation. This is unclear when applied to my example above. ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue24612> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
