Comparisons and sorting of a numeric class....
Steven D'Aprano
steve+comp.lang.python at pearwood.info
Sat Jan 24 00:01:09 EST 2015
Rustom Mody wrote:
> On Friday, January 23, 2015 at 10:22:06 PM UTC+5:30, Ian wrote:
>> On Fri, Jan 23, 2015 at 8:31 AM, Rustom Mody wrote:
>> > Can you tell me what of the following code does not satisfy your
>> > requirements?
>> > [Needs python 3.4]
>> >
>> >
>> >>>> from enum import IntEnum
>> >>>> class B4(IntEnum):
>> > F1 = 0
>> > F2 = 0
>> > F3 = 0
>> > T = 1
>>
>> This strikes me as a potential problem:
>>
>> >>> B4.F1 is B4.F2 is B4.F3
>> True
>> >>> list(B4)
>> [<B4.F1: 0>, <B4.T: 1>]
>>
>> Enum members with the same values are just aliases for one another,
>> not distinct entities.
>
> Yeah....
>
> The only workaround I have been able to come up with is:
>
> class B4(IntEnum):
>> F1 = 0
>> F2 = ""
>> F3 = None
>> T = 1
>
> which is not bad; its ridiculous
> [Like going around with a broken broom searching for falsey objects :-) ]
It certainly is. But fortunately it is not necessary.
# Untested
class B4(IntEnum):
F1 = 0
F2 = 1
F3 = 2
T = 3
def __bool__(self):
return self is B4.T
def __str__(self):
if self is B4.F1: return "Certainly False"
if self is B4.F2: return "Maybe False"
if self is B4.F3: return "Maybe True"
if self is B4.T: return "Certainly True"
--
Steven
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