1 # Class Date supplies date objects that support date arithmetic. 2 # 3 # Date(month,day,year) returns a Date object. An instance prints as, 4 # e.g., 'Mon 16 Aug 1993'. 5 # 6 # Addition, subtraction, comparison operators, min, max, and sorting 7 # all work as expected for date objects: int+date or date+int returns 8 # the date `int' days from `date'; date+date raises an exception; 9 # date-int returns the date `int' days before `date'; date2-date1 returns 10 # an integer, the number of days from date1 to date2; int-date raises an 11 # exception; date1 < date2 is true iff date1 occurs before date2 (& 12 # similarly for other comparisons); min(date1,date2) is the earlier of 13 # the two dates and max(date1,date2) the later; and date objects can be 14 # used as dictionary keys. 15 # 16 # Date objects support one visible method, date.weekday(). This returns 17 # the day of the week the date falls on, as a string. 18 # 19 # Date objects also have 4 read-only data attributes: 20 # .month in 1..12 21 # .day in 1..31 22 # .year int or long int 23 # .ord the ordinal of the date relative to an arbitrary staring point 24 # 25 # The Dates module also supplies function today(), which returns the 26 # current date as a date object. 27 # 28 # Those entranced by calendar trivia will be disappointed, as no attempt 29 # has been made to accommodate the Julian (etc) system. On the other 30 # hand, at least this package knows that 2000 is a leap year but 2100 31 # isn't, and works fine for years with a hundred decimal digits <wink>. 32 33 # Tim Peters tim (at] ksr.com 34 # not speaking for Kendall Square Research Corp 35 36 # Adapted to Python 1.1 (where some hacks to overcome coercion are unnecessary) 37 # by Guido van Rossum 38 39 # Note that as of Python 2.3, a datetime module is included in the stardard 40 # library. 41 42 # vi:set tabsize=8: 43 44 _MONTH_NAMES = [ 'January', 'February', 'March', 'April', 'May', 45 'June', 'July', 'August', 'September', 'October', 46 'November', 'December' ] 47 48 _DAY_NAMES = [ 'Friday', 'Saturday', 'Sunday', 'Monday', 49 'Tuesday', 'Wednesday', 'Thursday' ] 50 51 _DAYS_IN_MONTH = [ 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 ] 52 53 _DAYS_BEFORE_MONTH = [] 54 dbm = 0 55 for dim in _DAYS_IN_MONTH: 56 _DAYS_BEFORE_MONTH.append(dbm) 57 dbm = dbm + dim 58 del dbm, dim 59 60 _INT_TYPES = type(1), type(1L) 61 62 def _is_leap(year): # 1 if leap year, else 0 63 if year % 4 != 0: return 0 64 if year % 400 == 0: return 1 65 return year % 100 != 0 66 67 def _days_in_year(year): # number of days in year 68 return 365 + _is_leap(year) 69 70 def _days_before_year(year): # number of days before year 71 return year*365L + (year+3)//4 - (year+99)//100 + (year+399)//400 72 73 def _days_in_month(month, year): # number of days in month of year 74 if month == 2 and _is_leap(year): return 29 75 return _DAYS_IN_MONTH[month-1] 76 77 def _days_before_month(month, year): # number of days in year before month 78 return _DAYS_BEFORE_MONTH[month-1] + (month > 2 and _is_leap(year)) 79 80 def _date2num(date): # compute ordinal of date.month,day,year 81 return _days_before_year(date.year) + \ 82 _days_before_month(date.month, date.year) + \ 83 date.day 84 85 _DI400Y = _days_before_year(400) # number of days in 400 years 86 87 def _num2date(n): # return date with ordinal n 88 if type(n) not in _INT_TYPES: 89 raise TypeError, 'argument must be integer: %r' % type(n) 90 91 ans = Date(1,1,1) # arguments irrelevant; just getting a Date obj 92 del ans.ord, ans.month, ans.day, ans.year # un-initialize it 93 ans.ord = n 94 95 n400 = (n-1)//_DI400Y # # of 400-year blocks preceding 96 year, n = 400 * n400, n - _DI400Y * n400 97 more = n // 365 98 dby = _days_before_year(more) 99 if dby >= n: 100 more = more - 1 101 dby = dby - _days_in_year(more) 102 year, n = year + more, int(n - dby) 103 104 try: year = int(year) # chop to int, if it fits 105 except (ValueError, OverflowError): pass 106 107 month = min(n//29 + 1, 12) 108 dbm = _days_before_month(month, year) 109 if dbm >= n: 110 month = month - 1 111 dbm = dbm - _days_in_month(month, year) 112 113 ans.month, ans.day, ans.year = month, n-dbm, year 114 return ans 115 116 def _num2day(n): # return weekday name of day with ordinal n 117 return _DAY_NAMES[ int(n % 7) ] 118 119 120 class Date: 121 def __init__(self, month, day, year): 122 if not 1 <= month <= 12: 123 raise ValueError, 'month must be in 1..12: %r' % (month,) 124 dim = _days_in_month(month, year) 125 if not 1 <= day <= dim: 126 raise ValueError, 'day must be in 1..%r: %r' % (dim, day) 127 self.month, self.day, self.year = month, day, year 128 self.ord = _date2num(self) 129 130 # don't allow setting existing attributes 131 def __setattr__(self, name, value): 132 if self.__dict__.has_key(name): 133 raise AttributeError, 'read-only attribute ' + name 134 self.__dict__[name] = value 135 136 def __cmp__(self, other): 137 return cmp(self.ord, other.ord) 138 139 # define a hash function so dates can be used as dictionary keys 140 def __hash__(self): 141 return hash(self.ord) 142 143 # print as, e.g., Mon 16 Aug 1993 144 def __repr__(self): 145 return '%.3s %2d %.3s %r' % ( 146 self.weekday(), 147 self.day, 148 _MONTH_NAMES[self.month-1], 149 self.year) 150 151 # Python 1.1 coerces neither int+date nor date+int 152 def __add__(self, n): 153 if type(n) not in _INT_TYPES: 154 raise TypeError, 'can\'t add %r to date' % type(n) 155 return _num2date(self.ord + n) 156 __radd__ = __add__ # handle int+date 157 158 # Python 1.1 coerces neither date-int nor date-date 159 def __sub__(self, other): 160 if type(other) in _INT_TYPES: # date-int 161 return _num2date(self.ord - other) 162 else: 163 return self.ord - other.ord # date-date 164 165 # complain about int-date 166 def __rsub__(self, other): 167 raise TypeError, 'Can\'t subtract date from integer' 168 169 def weekday(self): 170 return _num2day(self.ord) 171 172 def today(): 173 import time 174 local = time.localtime(time.time()) 175 return Date(local[1], local[2], local[0]) 176 177 class DateTestError(Exception): 178 pass 179 180 def test(firstyear, lastyear): 181 a = Date(9,30,1913) 182 b = Date(9,30,1914) 183 if repr(a) != 'Tue 30 Sep 1913': 184 raise DateTestError, '__repr__ failure' 185 if (not a < b) or a == b or a > b or b != b: 186 raise DateTestError, '__cmp__ failure' 187 if a+365 != b or 365+a != b: 188 raise DateTestError, '__add__ failure' 189 if b-a != 365 or b-365 != a: 190 raise DateTestError, '__sub__ failure' 191 try: 192 x = 1 - a 193 raise DateTestError, 'int-date should have failed' 194 except TypeError: 195 pass 196 try: 197 x = a + b 198 raise DateTestError, 'date+date should have failed' 199 except TypeError: 200 pass 201 if a.weekday() != 'Tuesday': 202 raise DateTestError, 'weekday() failure' 203 if max(a,b) is not b or min(a,b) is not a: 204 raise DateTestError, 'min/max failure' 205 d = {a-1:b, b:a+1} 206 if d[b-366] != b or d[a+(b-a)] != Date(10,1,1913): 207 raise DateTestError, 'dictionary failure' 208 209 # verify date<->number conversions for first and last days for 210 # all years in firstyear .. lastyear 211 212 lord = _days_before_year(firstyear) 213 y = firstyear 214 while y <= lastyear: 215 ford = lord + 1 216 lord = ford + _days_in_year(y) - 1 217 fd, ld = Date(1,1,y), Date(12,31,y) 218 if (fd.ord,ld.ord) != (ford,lord): 219 raise DateTestError, ('date->num failed', y) 220 fd, ld = _num2date(ford), _num2date(lord) 221 if (1,1,y,12,31,y) != \ 222 (fd.month,fd.day,fd.year,ld.month,ld.day,ld.year): 223 raise DateTestError, ('num->date failed', y) 224 y = y + 1 225 226 if __name__ == '__main__': 227 test(1850, 2150) 228
