[Python-ideas] bool(datetime.time(0, 0))

[M.-A. Lemburg]

Antoine Pitrou wrote:
> On Tue, 08 May 2012 12:34:32 +0200
> "M.-A. Lemburg" <mal at egenix.com> wrote:
>>
>> Fully agreed.
>>
>> The above code is just plain wrong and often causes problems
>> in larger applications - besides, it's also slower in most
>> cases, esp. if determining the length of an object or
>> converting it to a numeric value is slow.
>>
>> If you want to test for None return values, you need to use
>> "if is None" or "if is not None".
> 
> So who writes the PEP to deprecate __bool__ methods wholesale?

I think I lost you there. What does the above have to do with
__bool__ methods ?

Whether or not a type implements the notion of a boolean value
is really up to the specific implementation and not a question
that can be answered in general.

It's perfectly fine for time value to mimic a boolean value
by following the same paradigm as a float "seconds since midnight"
value.

As such, reusing the __nonzero__ or __len__ slots for boolean
values is fine as well. It may not always make sense in every
conceivable way, but as long as there is a valid explanation
that can be documented, I don't see that as problem.

If you're purist, you'd probably disallow __bool__ methods
on non-boolean types, but this is Python, so we pass on
control to object and type implementers.

-- 
Marc-Andre Lemburg
eGenix.com

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