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

Alexander Belopolsky alexander.belopolsky at gmail.com
Thu Mar 6 17:13:57 CET 2014 
On Thu, Mar 6, 2014 at 8:21 AM, M.-A. Lemburg <mal at egenix.com> wrote:

> > Are they all False? No, no they're not (unless your local timezone is
> UTC):
> >
> >>>> bool(utcmidnight)
> > False
> >>>> bool(naivemidnight)
> > False
> >>>> bool(localmidnight)
> > True
>
> Now this is a what I consider a valid argument for making a change.


FWIW, I would be +0 for making a change so that t.tzinfo is not None
implies bool(t.timetz()) is True.

My intuition goes like this.  Given

>>> from datetime import *
>>> t1 = datetime(2014, 1, 1)
>>> t2 = datetime(2014, 1, 1, 12)
>>> t3 = datetime(2014, 1, 1, tzinfo=timezone.utc)

Instance t1 has no time information, so t1.time() is false-y.  Instance t2
has time information, so t2.time() is true-y.  Instance t3 is such that
t3.time() == t1.time(), but t3.timetz() has an additional information

>>> t3.timetz()
datetime.time(0, 0, tzinfo=datetime.timezone.utc)
>>> t3.time()
datetime.time(0, 0)

So t3.timetz() is not the same object as returned by the constructor with
no arguments - time().
This is reason enough to make it true-y.

This also does not affect my use-case because t3.time() is still false-y in
this logic:

>>> [bool(t) for t in [t1.time(), t2.time(), t3.time(), time()]]
[False, True, False, False]

Which is consistent with

>>> t3.time() == t1.time() == time()
True
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