compute federal holidays - from Mike P

src/perryman/holidays.py

@@ -0,0 +1,99 @@
+import calendar, datetime, sys
+
+try    : year = int(sys.argv[1])
+except : year = datetime.datetime.now().year
+
+Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday = range(7);
+dayNames = ["Monday","Tuesday","Wednesday","Thursday","Friday","Saturday","Sunday"]
+monthNames = ["!!!!","January","February","March","April","May","June","July","August","September","October","November","December"]
+
+federalHolidayNames = [
+#  These are the official names by law
+#  ---------------------------------------
+   "New Year's Day",
+   "Birthday of Martin Luther King, Jr.",
+   "Washington's Birthday",
+   "Memorial Day",
+   "Independence Day",
+   "Labor Day",
+   "Columbus Day",
+   "Veterans Day",
+   "Thanksgiving Day",
+   "Christmas Day"
+]
+
+def adjustToWeekday(date) :
+   '''
+   Return the nearest weekday (Mon - Fri) to the specified date
+   '''
+   weekday = date.weekday()
+   if weekday == Saturday :
+      date -= datetime.timedelta(1)
+   elif weekday == Sunday :
+      date += datetime.timedelta(1)
+   return date
+
+def ordinalStr(number) :
+   '''
+   Format a number as an ordinal string
+   '''
+   if number == -1 : 
+      return "last"
+   else :
+      digit = number % 10
+      if   digit == 1 : return "%dst" % number
+      elif digit == 2 : return "%dnd" % number   
+      elif digit == 3 : return "%drd" % number
+      else            : return "%dth" % number   
+
+def nthWeekday(n, weekday, month, year) : 
+   '''
+   Return the nth specified weekday of the specified month and year
+   '''
+   weeks = calendar.monthcalendar(year, month)
+   if n == -1 :
+      for i in range(len(weeks))[::-1] :
+         if weeks[i][weekday] != 0 : return datetime.date(year, month, weeks[i][weekday])
+   else :
+      count = 0
+      for week in weeks :
+         if week[weekday] != 0 : count += 1
+         if count == n : return datetime.date(year, month, week[weekday])
+      raise ValueError("%s, %d has no %s %s" % (monthNames[month], year, ordinalStr(n), dayNames[weekday]))      
+
+def getHolidayDate(holidayName, year) :
+   '''
+   Return the date that the federal holiday is celebrated in the specified year
+   '''
+   if   holidayName == federalHolidayNames[0] : return adjustToWeekday(datetime.date(year, 1, 1))
+   elif holidayName == federalHolidayNames[1] : return nthWeekday(3, Monday, 1, year)
+   elif holidayName == federalHolidayNames[2] : return nthWeekday(3, Monday, 2, year)
+   elif holidayName == federalHolidayNames[3] : return nthWeekday(-1, Monday, 5, year)
+   elif holidayName == federalHolidayNames[4] : return adjustToWeekday(datetime.date(year, 7, 4))
+   elif holidayName == federalHolidayNames[5] : return nthWeekday(1, Monday, 9, year)
+   elif holidayName == federalHolidayNames[6] : return nthWeekday(2, Monday, 10, year)
+   elif holidayName == federalHolidayNames[7] : return adjustToWeekday(datetime.date(year, 11, 11))
+   elif holidayName == federalHolidayNames[8] : return nthWeekday(4, Thursday, 11, year)
+   elif holidayName == federalHolidayNames[9] : return adjustToWeekday(datetime.date(year, 12, 25))
+   else : raise ValueError("Unknown holiday name: %s" % holidayName)
+
+def getAllHolidays(year) :
+   '''
+   Return a dictionary of all federal holiday in the specified year
+   '''
+   holidays = {}
+   for holidayName in federalHolidayNames :
+      date = getHolidayDate(holidayName, year)
+      if date.year == year : holidays[date] = holidayName
+   holidayName = federalHolidayNames[0]      
+   date = getHolidayDate(holidayName, year+1)
+   if date.year == year : holidays[date] = holidayName
+   return holidays   
+
+def main() :   
+   print("Federal holidays in %d" % year)
+   holidays = getAllHolidays(year)
+   for date in sorted(holidays.keys()) :
+      print("\t%s : %s" % (date.strftime("%a, %d %b %Y"), holidays[date]))
+
+if __name__ == "__main__" : main()