Why does datetime.timedelta only have the attributes 'days' and 'seconds'?

[Chris Angelico]

On Fri, 15 Apr 2022 at 00:54, Loris Bennett <loris.bennett at fu-berlin.de> wrote:
>
> Hi,
>
> With Python 3.9.2 I get
>
>   $ import datetime
>   $ s = "1-00:01:01"
>   $ t = datetime.datetime.strptime(s, "%d-%H:%M:%S")
>   $ d = datetime.timedelta(days=t.day, hours=t.hour, minutes=t.minute, seconds=t.second)
>   $ d.days
>   1
>   $ d.seconds
>   61
>   $ d.minutes
>   AttributeError: 'datetime.timedelta' object has no attribute 'minutes'
>
> Is there a particular reason why there are no attributes 'minutes' and
> 'hours and the attribute 'seconds' encompasses is the entire fractional
> day?
>

You can get those by dividing:

>>> divmod(d, datetime.timedelta(minutes=1))
(1441, datetime.timedelta(seconds=1))

But the obvious question is: how many minutes ARE there in this time
period? I give a response of 1441 (or if you prefer, 1441 + 1/60 or
roughly 1441.017), but you might just as reasonably consider that
there is one minute.

If a good definition could be chosen, it wouldn't be too hard to add a
bunch of properties to the timedelta that let you view it in other
ways. Otherwise, the easiest way is probably to define yourself a set
of units and sequentially divmod:

>>> units = {"days": datetime.timedelta(days=1), "hours": datetime.timedelta(hours=1), "minutes": datetime.timedelta(minutes=1), "seconds": datetime.timedelta(seconds=1)}
>>> for label, unit in units.items():
...     n, d = divmod(d, unit)
...     print(n, label)
...
1 days
0 hours
1 minutes
1 seconds
>>>

This way, you have full control over which units are "interesting";
for instance, the constructor supports weeks, but a lot of
applications won't consider them to be important, and would prefer to
see "20 days" than "2 weeks and 6 days".

But, as mentioned, adding properties to timedelta would be a
relatively benign change, so it could be done if there's enough need
and a good definition.

ChrisA