[Tutor] time comparison question

Liam Clarke cyresse at gmail.com
Fri Nov 26 12:56:43 CET 2004

Hi Brian, 

I was in a similar position to you 3 weeks ago, and I was using
time.time, and time.gmtime.

Each of these returns a 9 value tuple, which is documented deep within
the time module.

The 9 value tuple has year to microsecond, and day of the week
contained, so you can use it if you wish.

 I'm in the same boat as you, regarding OOP, although I use it when
suitable, and all I've got to say is - what's the big deal? I can see
it would be useful for certain applications, but it's nothing
lifechanging, unlike Python :D

I would recommend biting the bullet and using a date/time object. You
don't need to grok OOP to use it, and it makes this easier.

 May I post some code to demonstrate?

I wanted to write code which would find out what date last Friday was,
whenever the code was run.

Using time.gmtime, this is what I accomplished (kept for posteritie's
sake only..)
def getFriday(mail_offset):

       (year, month, day, weekday)=gm_data[0], gm_data[1], gm_data[2],
       date_offset= -(mail_offset-weekday) 
       last_friday=datetime.date(year, month, day) -
       email_sent_date=time.strftime("%d-%b-%Y", (int(split_date[0]),
int(split_date[1]), int(split_date[2]), 0, 0, 0, 0, 0, 0))

       return email_sent_date

Now, i posted this up to this list, Kent Johnson recommended this instead- 

def getFriday(day):
    lastFriday = datetime.date.today()
    oneday = datetime.timedelta(days=1)

    while lastFriday.weekday() != day:
        lastFriday -= oneday

    return lastFriday.strftime('%d-%b-%Y')

Both returned a date in the format 15-Oct-2004

Guess which one I went with?
My original code was brute forcish, unmaintainable & ugly, but it
worked when I wrote it. Sounds like Perl really. But notice that I had
to use an object anyway to invoke timedelta, so all my messing around
was in vain.

Highly recommend this - 

a) Use the datetime module
b) Use datetime objects, so you don't have to mess around with
functions that require 9 digit tuples
c) Listen to Kent if he posts, he's good. 

Give datetime a try, and see how it goes.

Good luck,

Liam Clarke

On Fri, 26 Nov 2004 04:45:53 -0500, Brian van den Broek
<bvande at po-box.mcgill.ca> wrote:
> Hi all,
> I'm trying to build some Python 2.3.4 code which will determine if the
> actual time when it is run is after the date and time specified in some
> data. I want my data to be able to specify the target date/time in a
> various levels of detail. I.e., I want 2004-11-28 13:25, 2004-11-28,
> 11-28, 11-28 13:25 to all be accepted.
> My first thought was to get the current time via time.time() and then
> parse my target date into a struct_time tuple to pass to time.mktime(),
> run a comparison and be done. However, a struct_time tuple has data that
> I won't know, given one of my target dates. I can make sensible dummies
> for seconds (as well as year, hours and minutes when my target does not
> specify them), and I know that the time module will try to make a
> reasonable guess if given -1 for the DST element. But for
> a_struct_time_tuple[-3:-1], I'd just be guessing at the weekday and day
> of year. This leads to two questions:
> 1) As I write, time.asctime() gives 'Fri Nov 26 04:32:18 2004' for a
> time.localtime() of (2004, 11, 26, 4, 32, 18, 4, 331, 0). If I were
> filling out a target date of 2004-11-26 04:32, I might well end up
> passing something like (2004, 11, 26, 4, 32, 18, 6, 328, 0) to
> time.mktime() for the result 'Sun Nov 26 04:32:18 2004'. If I am not
> actually using the weekday information, I suspect that I can just ignore
> the incorrect 'Sun'. But I feel better checking -- is anything going to
> break by giving struct_time elements that don't make sense (provided of
> course I am not myself explicitly drawing upon them)?
> 2) Naturally, these worries lead me to think that there must be a better
> way. I took a brief look at the datetime module, thinking it was a
> natural place to find such tools. But it is all in terms of classes.
> Sadly, I am still not too comfortable with doing things via OOP, so I'd
> prefer a procedural (if that's the right term for a program with
> functions but no classes) way. Is there a cleaner, non-class employing,
> way of meeting my goal of finding out if a date of the form YYYY-MM-DD
> is in the future, present, or past? (If it matters, I am on Windows.)
> Thanks for any links, etc.
> Best to all,
> Brian vdB
> _______________________________________________
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> http://mail.python.org/mailman/listinfo/tutor

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