[Tutor] time comparison question

[Liam Clarke]

Hi Brian, 

class datetime( year, month, day, hour=0, minute=0, second=0,
microsecond=0, tzinfo=None)


Ease of use demo -

>>>import datetime
>>>date1 = datetime.datetime(2001,11,11,12)
>>>print str(date1)
2001-11-11 12:00:00

>>>date2 = datetime.datetime(2007,10,10,9,20,20,20)
>>>print str(date2)
2007-10-10 09:20:20.000020

>>>print date1.strftime('"%d-%b-%Y"')
11-Nov-2001

>>>date2.strftime('"%A, %d %B %Y. Time is %X"')
Wednesday, 10 October 2007. Time is 09:20:20

>>>print "difference between",date1,"&",date2
difference between 2001-11-11 12:00:00 & 2007-10-10 09:20:20.000020

>>> print date1-date2
-2159 days, 2:39:39.999980

>>> print "difference between",date2,"&",date1
difference between 2007-10-10 09:20:20.000020 & 2001-11-11 12:00:00

>>>print date2-date1
2158 days, 21:20:20.000020

>>>dateDif=date2-date1
>>>type(dateDif)
<type 'datetime.timedelta'>

So yeah, poke around, it'll do pretty much everything date related you need.

Oh, and for your particular problem - so if 10/10/2007 minus
11/11/2001 is a positive value, then you know that all future dates
will have a positive difference. Past dates will be negative
difference, and it'd be very unlikely that you'd get a zero value, but
it's possible.

HTH

Liam Clarke

On Sat, 27 Nov 2004 00:56:43 +1300, Liam Clarke <cyresse at gmail.com> wrote:
> 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):
> 
>        gm_data=time.gmtime()
>        (year, month, day, weekday)=gm_data[0], gm_data[1], gm_data[2],
> gm_data[6]
>        date_offset= -(mail_offset-weekday)
>        last_friday=datetime.date(year, month, day) -
> datetime.timedelta(days=date_offset)
>        retrieve_date_string=str(last_friday)
>        split_date=retrieve_date_string.split('-')
>        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
> >
> > _______________________________________________
> > Tutor maillist  -  Tutor at python.org
> > http://mail.python.org/mailman/listinfo/tutor
> >
> 
> 
> --
> 'There is only one basic human right, and that is to do as you damn well please.
> And with it comes the only ba sic human duty, to take the consequences.
> 


-- 
'There is only one basic human right, and that is to do as you damn well please.
And with it comes the only basic human duty, to take the consequences.