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

[M.-A. Lemburg]

On 06.03.2014 03:23, Donald Stufft wrote:
> 
> On Mar 5, 2014, at 9:15 PM, Tim Peters <tim.peters at gmail.com> wrote:
> 
>> [Donald Stufft]
>>> When the documented behavior is both nonsensical and the cause of hard to debug bugs that
>>> is a pretty compelling use case to me, unless you actively enjoy being user hostile.
>> 
>> Breaking code that currently works is as hostile as hostile gets. Where is the evidence that
>> no code relies on the current behavior? For that matter, where is the evidence that the
>> current behavior is a significant cause of bugs?  I know I've used "if some_time_object:", 
>> but it did exactly what I expected it to do.
> 
> Forgive me if I’m wrong, but aren’t you the author of the date time module? If that’s the case
> what you expect it to do isn’t particularly relevant as you’re intimately aware of it’s
> implementation.

Just in case you're looking for a relevant use case:

Having bool(time(0,0,0)) allows you to quickly check whether you are
dealing with a datetime value with (non-trivial) time part or not.

You run into situations where you have to test for this in
date/time conversions, arithmetics, etc. e.g. if you need to convert
a datetime value to a date and want to prevent truncation of
information, or if you want to format a datetime value in a user
friendly way by omitting the zero time part, or if you're doing
datetime arithmetic that has to follow special requirements w/r to
days (think interest or insurance math) and you want to
quickly check whether you can use the fast path simple
calculation, or you need to do the full blown complicated part.

Now, those use cases may still not appear relevant to you, but then
the argument that "if x:" should not trigger for time(0,0,0)
because x might actually be None, is also not relevant to me,
since it masks a bug in the example code and those should never
go undetected :-)

-- 
Marc-Andre Lemburg
eGenix.com

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