[Tutor] Readable date arithmetic

[Kent Johnson]

On Thu, Nov 19, 2009 at 1:14 AM, Stephen Nelson-Smith
<sanelson at gmail.com> wrote:
> I have the following method:
>
> def get_log_dates(the_date_we_want_data_for):
>  t = time.strptime(the_date_we_want_data_for, '%Y%m%d')
>  t2 = datetime.datetime(*t[:-2])

Use datetime.datetime.strptime() to save a step:
t2 = datetime.datetime.strptime(the_date_we_want_data_for, '%Y%m%d')

>  extra_day = datetime.timedelta(days=1)
>  t3 = t2 + extra_day

t2 += datetime.timedelta(days=1)

>  next_log_date = t3.strftime('%Y%m%d')
>  return (the_date_we_want_data_for, next_log_date)
>
> Quite apart from not much liking the t[123] variables, does date
> arithmetic really need to be this gnarly?

Yes, pretty much. Convert the string to a date-aware object, increment
the date, convert back to a string.

> How could I improve the above, especially from a readability
> perspective?

Above changes improve readability IMO.

Kent