469,579 Members | 1,198 Online
Bytes | Developer Community
New Post

Home Posts Topics Members FAQ

Post your question to a community of 469,579 developers. It's quick & easy.

Getting start/end dates given week-number

I've been trying to come up with a good algorithm for determining
the starting and ending dates given the week number (as defined
by the strftime("%W") function).

My preference would be for a Sunday->Saturday range rather than a
Monday->Sunday range. Thus,
startDate, stopDate = weekBoundaries(2006, 23)


would yield a start-date of June 4, 2006 and an end-date of June
10, 2006 in this hypothetical function (as strftime("%W") for
today, June 9th, 2006 returns 23).

I've posted my first round of code below, but I'm having problems
with dates early in 2005, as the tests show.

Any thoughts/improvements/suggestions would be most welcome.

Thanks,

-tkc
from datetime import date, timedelta
from time import strptime
DEBUG = False
tests = [
#test date start end
(date(2006,1,1), (date(2006,1,1), date(2006,1,7))),
(date(2006,1,2), (date(2006,1,1), date(2006,1,7))),
(date(2006,1,3), (date(2006,1,1), date(2006,1,7))),
(date(2006,1,4), (date(2006,1,1), date(2006,1,7))),
(date(2006,1,5), (date(2006,1,1), date(2006,1,7))),
(date(2006,1,6), (date(2006,1,1), date(2006,1,7))),
(date(2006,1,7), (date(2006,1,1), date(2006,1,7))),
(date(2006,1,8), (date(2006,1,8), date(2006,1,14))),
(date(2005,1,1), (date(2004,12,26), date(2005,1,1))),
(date(2005,1,2), (date(2005,1,2), date(2005,1,8))),
]
def weekBoundaries(year, week):
startOfYear = date(year, 1, 1)
now = startOfYear + timedelta(weeks=week)
# isoweekday() % 7 returns Sun=0 ... Sat=6
sun = now - timedelta(days=now.isoweekday() % 7)
sat = sun + timedelta(days=6)
if DEBUG:
print "DEBUG: now = %s/%s" % (now, now.strftime("%a"))
print "DEBUG: sun = %s/%s" % (sun, sun.strftime("%a"))
print "DEBUG: sat = %s/%s" % (sat, sat.strftime("%a"))
return sun, sat

for test, expectedResult in tests:
print "Testing %s" % test
year = test.year
# jigger it so that %W is Sun->Sat rather than Mon->Sun
weekNum = int((test + timedelta(days=1)).strftime("%W")) - 1
results = weekBoundaries(year, weekNum)
passed = (expectedResult == results)
print "Week#%s: %s" % (weekNum, passed)
print "=" * 50


Jun 9 '06 #1
3 16204
see the calendar faq http://www.faqs.org/faqs/calendars/faq/part3/,
look especially in section 6.7.

Tim Chase wrote:
I've been trying to come up with a good algorithm for determining
the starting and ending dates given the week number (as defined
by the strftime("%W") function).

My preference would be for a Sunday->Saturday range rather than a
Monday->Sunday range. Thus,
>>> startDate, stopDate = weekBoundaries(2006, 23)


would yield a start-date of June 4, 2006 and an end-date of June
10, 2006 in this hypothetical function (as strftime("%W") for
today, June 9th, 2006 returns 23).

I've posted my first round of code below, but I'm having problems
with dates early in 2005, as the tests show.

Any thoughts/improvements/suggestions would be most welcome.

Thanks,

-tkc
from datetime import date, timedelta
from time import strptime
DEBUG = False
tests = [
#test date start end
(date(2006,1,1), (date(2006,1,1), date(2006,1,7))),
(date(2006,1,2), (date(2006,1,1), date(2006,1,7))),
(date(2006,1,3), (date(2006,1,1), date(2006,1,7))),
(date(2006,1,4), (date(2006,1,1), date(2006,1,7))),
(date(2006,1,5), (date(2006,1,1), date(2006,1,7))),
(date(2006,1,6), (date(2006,1,1), date(2006,1,7))),
(date(2006,1,7), (date(2006,1,1), date(2006,1,7))),
(date(2006,1,8), (date(2006,1,8), date(2006,1,14))),
(date(2005,1,1), (date(2004,12,26), date(2005,1,1))),
(date(2005,1,2), (date(2005,1,2), date(2005,1,8))),
]
def weekBoundaries(year, week):
startOfYear = date(year, 1, 1)
now = startOfYear + timedelta(weeks=week)
# isoweekday() % 7 returns Sun=0 ... Sat=6
sun = now - timedelta(days=now.isoweekday() % 7)
sat = sun + timedelta(days=6)
if DEBUG:
print "DEBUG: now = %s/%s" % (now, now.strftime("%a"))
print "DEBUG: sun = %s/%s" % (sun, sun.strftime("%a"))
print "DEBUG: sat = %s/%s" % (sat, sat.strftime("%a"))
return sun, sat

for test, expectedResult in tests:
print "Testing %s" % test
year = test.year
# jigger it so that %W is Sun->Sat rather than Mon->Sun
weekNum = int((test + timedelta(days=1)).strftime("%W")) - 1
results = weekBoundaries(year, weekNum)
passed = (expectedResult == results)
print "Week#%s: %s" % (weekNum, passed)
print "=" * 50


Jun 9 '06 #2
Tim Chase wrote:
I've been trying to come up with a good algorithm for determining
the starting and ending dates given the week number (as defined
by the strftime("%W") function).
I think you missed %U format, since later you write:
My preference would be for a Sunday->Saturday range rather than a
Monday->Sunday range. Thus, Any thoughts/improvements/suggestions would be most welcome.


If you want to match %U:

def weekBoundaries(year, week):
startOfYear = date(year, 1, 1)
week0 = startOfYear - timedelta(days=startOfYear.isoweekday())
sun = week0 + timedelta(weeks=week)
sat = sun + timedelta(days=6)
return sun, sat

Jun 9 '06 #3
> I think you missed %U format, since later you write:

correct. I remember seeing something (a long while back) that
had a Sunday-first format, but I must have missed it in my
reading of "man strftime".
If you want to match %U:

def weekBoundaries(year, week):
startOfYear = date(year, 1, 1)
week0 = startOfYear - timedelta(days=startOfYear.isoweekday())
sun = week0 + timedelta(weeks=week)
sat = sun + timedelta(days=6)
return sun, sat


Works wonderfully...Thanks!

-tkc


Jun 9 '06 #4

This discussion thread is closed

Replies have been disabled for this discussion.

Similar topics

3 posts views Thread by Dave Griffiths | last post: by
5 posts views Thread by Bullschmidt | last post: by
6 posts views Thread by Bill R via AccessMonster.com | last post: by
reply views Thread by Lee Harr | last post: by
5 posts views Thread by Elainie | last post: by
reply views Thread by suresh191 | last post: by
By using this site, you agree to our Privacy Policy and Terms of Use.