Expressing time.

[Eddie Corns]

"Sean" <null-spam at tfh.ca> writes:

>I'm playing around times and dates.  I'd like to determine the age of
>particular sets of data in a user friendly matter.

>I've got everything ready but dealing with time in a user friendly manner.

>What would be a good way to express (in python):
>        time.localtime()+30 days
>        time.localtime()+5 minutes
>        time.localtime()+2 months
>        time.localtime()-2 years

>Is there any python facilities to make this an easier chore (aka
>time.localtime()+months(3))?
>(I included months as it is a special case in that you can't just
>arbitrarily calculate months in seconds without being relative to a
>particular month).

mx.DateTime makes these sort of calculations easy.  I have a similarish task
in presenting users an easy way of specifying which day's log files to search
(hence in this case it was always a date in the past but the principle would
be similar).  So I allow things like 'monday', 'tuesday' etc. and -n for n
days ago and several other variations.  The interesting one in this instance
is:

    dm_reg  = re.compile (r'^(-?\d\d?)[/.](-?\d\d?)$')
    this_day = today()

    # dd/mm (-ve dd means count from end of month, -mm is mm months ago)
    mt = re.match (dm_reg, user_input)
    if mt:
        dy,mon = map(int, mt.groups())
        if mon < 0:
            mon = this_day.month + mon
            if mon <= 0:
                mon = 12 + mon
        dt = DateTime (this_day.year, mon, dy)
        if dt > this_day:
            dt = DateTime (this_day.year-1, mon, dy)
        return dt

Which allows eg 1/-2 for the first of whatever month was 2 months ago or even
-1/-1 for the last day of the previous month.  mx.DateTime is doing all the
hard work.  You could cook up something similar to parse eg "-2m" "+2y" etc.

Possibly the new time stuff in 2.3 will do this also, I haven't looked at 2.3
yet.

Eddie