[Python-ideas] Changing the meaning of bool.__invert__

[Robert Kern]

On 2016-04-07 13:19, Oscar Benjamin wrote:
> On 7 April 2016 at 08:46, Antoine Pitrou <solipsis at pitrou.net> wrote:

>> Numpy's boolean type does the more useful (and more expected) thing:
>>
>>>>> ~np.bool_(True)
>> False
>
> This is a consequence of another unfortunate design by numpy. The
> reason for this is that numpy uses Python's bitwise operators to do
> element-wise logical operations.

This is not correct. & | ^ ~ are all genuine bitwise operations on numpy arrays.

 >>> i = np.arange(5)
 >>> ~i
array([-1, -2, -3, -4, -5])

What you are seeing with bool arrays is that bool arrays are *not* just uint8 
arrays. Each element happens to take up a single 8-bit byte, but only one of 
those bits contributes to its value; the other 7 bits are mere padding. The 
bitwise & | ^ ~ operators all work on that single bit correctly. They do not 
operate on the padding bits as they are not part of the bool's value.

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco