Minus operator versus unary minus
Peter Otten
__peter__ at web.de
Sat May 30 04:36:48 EDT 2015
Steven D'Aprano wrote:
> On Sat, 30 May 2015 05:56 pm, Peter Otten wrote:
>
>> The following modification of the collections.Counter implementation
>>
>> https://hg.python.org/cpython/rev/fe4efc0032b5
>>
>> was just checked in with the line
>>
>> result[elem] = 0 - count
>>
>> Does this have an advantage over the obvious
>>
>> result[elem] = -count
>>
>> ?
>
>
> py> class Thingy:
> ... def __neg__(self):
> ... return [1, 2, 3, 4]
> ...
> py> -Thingy()
> [1, 2, 3, 4]
> py> 0 - Thingy()
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> TypeError: unsupported operand type(s) for -: 'int' and 'Thingy'
Hm, do you have an example of a Counter (or subclass) instance where the
values are not int?
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