missing 'xor' Boolean operator

[Wayne Brehaut]

On 15 Jul 2009 09:11:44 GMT, Steven D'Aprano
<steven at REMOVE.THIS.cybersource.com.au> wrote:

>On Tue, 14 Jul 2009 11:25:08 -0700, Dr. Phillip M. Feldman wrote:
>
>> Current Boolean operators are 'and', 'or', and 'not'.  It would be nice
>> to have an 'xor' operator as well.
>
>I've often wished there was too, for the sake of completeness and 
>aesthetics, I'd love to be able to write:
>
>a xor b
>
>instead of defining a function xor(a, b).
>
>Unfortunately, outside of boolean algebra and simulating electrical 
>circuits, I can't think of any use-cases for an xor operator. Do you have 
>any?

Since xor in set theory is the symmetric difference,  perhaps we'd
like to know all items in exactly one of two word lists or
dictionaries, or anything else we could easily set-ize:

>>> cheese = set(['cheddar', 'limburger', 'stilton'])
>>> stinky = set(['skunk', 'limburger', 'stilton', 'polecat', 'doggy-doo', 'civet'])
>>> nasty = set(['doggy-doo', 'polecat', 'limburger', 'Perl'])
>>> cheese & stinky # stinky cheese
set(['limburger', 'stilton'])
>>> cheese ^ stinky # either cheese or stinky but not both
set(['doggy-doo', 'civet', 'polecat', 'skunk', 'cheddar'])
>>> cheese ^ stinky ^ nasty # in an odd number of these sets (1 or 3)
set(['civet', 'cheddar', 'Perl', 'limburger', 'skunk'])

Who hasn't needed that occasionally?

wayne