Getting start/end dates given week-number

[wittempj@hotmail.com]

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