[Python-ideas] Please reconsider the Boolean evaluation of midnight

[M.-A. Lemburg]

On 06.03.2014 12:04, M.-A. Lemburg wrote:
> On 06.03.2014 11:46, Antoine Pitrou wrote:
>> Le 06/03/2014 11:33, M.-A. Lemburg a écrit :
>>>
>>> I find it strange that the only argument against having time(0,0,0)
>>> evaluate to False in a boolean context is a wrongly used
>>> None test.
>>
>> It's only "wrongly used" because of that particular wart.
>> In other words, the "wrongly used" None test *exposes* the wart, it is not its *cause*.
> 
> Wait. Let's be clear on this:
> 
> Writing
> 
>     if x: print ('x is None')

The above is obviously wrong :-). Let's try again:

      if not x: print ('x is None')

> or
> 
>     if x == None: print ('x is None')
> 
> is wrong code.
> 
> None is a singleton, so you have to use the "is" operator, i.e.
> 
>     if x is None: print ('x is None')
> 
> is the only correct way of testing for None.
> 
> Adding a test to pylint for this would probably be more helpful
> and address the real problem in a more productive way, than the
> current discussion to making the above problematic code work in
> the single use case of x being a datetime.time object.
> 
>> There are other contexts with implicit boolean conversion, such as any() and all().
> 
> If you expect those to work correctly for None testing, then
> you're writing wrong code as well.
> 

-- 
Marc-Andre Lemburg
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