228 lines
7.5 KiB
Python
228 lines
7.5 KiB
Python
"""
|
|
Class Date supplies date objects that support date arithmetic.
|
|
|
|
Date(month,day,year) returns a Date object. An instance prints as,
|
|
e.g., 'Mon 16 Aug 1993'.
|
|
|
|
Addition, subtraction, comparison operators, min, max, and sorting
|
|
all work as expected for date objects: int+date or date+int returns
|
|
the date `int' days from `date'; date+date raises an exception;
|
|
date-int returns the date `int' days before `date'; date2-date1 returns
|
|
an integer, the number of days from date1 to date2; int-date raises an
|
|
exception; date1 < date2 is true iff date1 occurs before date2 (&
|
|
similarly for other comparisons); min(date1,date2) is the earlier of
|
|
the two dates and max(date1,date2) the later; and date objects can be
|
|
used as dictionary keys.
|
|
|
|
Date objects support one visible method, date.weekday(). This returns
|
|
the day of the week the date falls on, as a string.
|
|
|
|
Date objects also have 4 read-only data attributes:
|
|
.month in 1..12
|
|
.day in 1..31
|
|
.year int or long int
|
|
.ord the ordinal of the date relative to an arbitrary staring point
|
|
|
|
The Dates module also supplies function today(), which returns the
|
|
current date as a date object.
|
|
|
|
Those entranced by calendar trivia will be disappointed, as no attempt
|
|
has been made to accommodate the Julian (etc) system. On the other
|
|
hand, at least this package knows that 2000 is a leap year but 2100
|
|
isn't, and works fine for years with a hundred decimal digits <wink>.
|
|
|
|
Tim Peters tim@ksr.com
|
|
not speaking for Kendall Square Research Corp
|
|
|
|
Adapted to Python 1.1 (where some hacks to overcome coercion are unnecessary)
|
|
by Guido van Rossum
|
|
|
|
Note that as of Python 2.3, a datetime module is included in the stardard
|
|
library.
|
|
"""
|
|
|
|
import functools
|
|
|
|
_MONTH_NAMES = [ 'January', 'February', 'March', 'April', 'May',
|
|
'June', 'July', 'August', 'September', 'October',
|
|
'November', 'December' ]
|
|
|
|
_DAY_NAMES = [ 'Friday', 'Saturday', 'Sunday', 'Monday',
|
|
'Tuesday', 'Wednesday', 'Thursday' ]
|
|
|
|
_DAYS_IN_MONTH = [ 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 ]
|
|
|
|
_DAYS_BEFORE_MONTH = []
|
|
dbm = 0
|
|
for dim in _DAYS_IN_MONTH:
|
|
_DAYS_BEFORE_MONTH.append(dbm)
|
|
dbm = dbm + dim
|
|
del dbm, dim
|
|
|
|
def _is_leap(year): # 1 if leap year, else 0
|
|
if year % 4 != 0: return 0
|
|
if year % 400 == 0: return 1
|
|
return year % 100 != 0
|
|
|
|
def _days_in_year(year): # number of days in year
|
|
return 365 + _is_leap(year)
|
|
|
|
def _days_before_year(year): # number of days before year
|
|
return year*365 + (year+3)//4 - (year+99)//100 + (year+399)//400
|
|
|
|
def _days_in_month(month, year): # number of days in month of year
|
|
if month == 2 and _is_leap(year): return 29
|
|
return _DAYS_IN_MONTH[month-1]
|
|
|
|
def _days_before_month(month, year): # number of days in year before month
|
|
return _DAYS_BEFORE_MONTH[month-1] + (month > 2 and _is_leap(year))
|
|
|
|
def _date2num(date): # compute ordinal of date.month,day,year
|
|
return _days_before_year(date.year) + \
|
|
_days_before_month(date.month, date.year) + \
|
|
date.day
|
|
|
|
_DI400Y = _days_before_year(400) # number of days in 400 years
|
|
|
|
def _num2date(n): # return date with ordinal n
|
|
if not isinstance(n, int):
|
|
raise TypeError('argument must be integer: %r' % type(n))
|
|
|
|
# Get uninitialized Date object. This is necesary because once
|
|
# attributes are set, they cannot be changed.
|
|
ans = Date.__new__(Date)
|
|
ans.ord = n
|
|
|
|
n400 = (n-1)//_DI400Y # # of 400-year blocks preceding
|
|
year, n = 400 * n400, n - _DI400Y * n400
|
|
more = n // 365
|
|
dby = _days_before_year(more)
|
|
if dby >= n:
|
|
more = more - 1
|
|
dby = dby - _days_in_year(more)
|
|
year, n = year + more, n - dby
|
|
month = min(n//29 + 1, 12)
|
|
dbm = _days_before_month(month, year)
|
|
if dbm >= n:
|
|
month = month - 1
|
|
dbm = dbm - _days_in_month(month, year)
|
|
|
|
ans.month, ans.day, ans.year = month, n-dbm, year
|
|
return ans
|
|
|
|
def _num2day(n): # return weekday name of day with ordinal n
|
|
return _DAY_NAMES[n % 7]
|
|
|
|
@functools.total_ordering
|
|
class Date:
|
|
def __init__(self, month, day, year):
|
|
if not 1 <= month <= 12:
|
|
raise ValueError('month must be in 1..12: %r' % (month,))
|
|
dim = _days_in_month(month, year)
|
|
if not 1 <= day <= dim:
|
|
raise ValueError('day must be in 1..%r: %r' % (dim, day))
|
|
self.month, self.day, self.year = map(int, (month, day, year))
|
|
self.ord = _date2num(self)
|
|
|
|
# don't allow setting existing attributes
|
|
def __setattr__(self, name, value):
|
|
if name in self.__dict__:
|
|
raise AttributeError('read-only attribute ' + name)
|
|
self.__dict__[name] = value
|
|
|
|
def __eq__(self, other):
|
|
return self.ord == other.ord
|
|
|
|
def __lt__(self, other):
|
|
return self.ord < other.ord
|
|
|
|
# define a hash function so dates can be used as dictionary keys
|
|
def __hash__(self):
|
|
return hash(self.ord)
|
|
|
|
# print as, e.g., Mon 16 Aug 1993
|
|
def __repr__(self):
|
|
return '%.3s %2d %.3s %r' % (
|
|
self.weekday(),
|
|
self.day,
|
|
_MONTH_NAMES[self.month-1],
|
|
self.year)
|
|
|
|
# Python 1.1 coerces neither int+date nor date+int
|
|
def __add__(self, n):
|
|
if not isinstance(n, int):
|
|
raise TypeError('can\'t add %r to date' % type(n))
|
|
return _num2date(self.ord + n)
|
|
__radd__ = __add__ # handle int+date
|
|
|
|
# Python 1.1 coerces neither date-int nor date-date
|
|
def __sub__(self, other):
|
|
if isinstance(other, int): # date-int
|
|
return _num2date(self.ord - other)
|
|
else:
|
|
return self.ord - other.ord # date-date
|
|
|
|
# complain about int-date
|
|
def __rsub__(self, other):
|
|
raise TypeError('Can\'t subtract date from integer')
|
|
|
|
def weekday(self):
|
|
return _num2day(self.ord)
|
|
|
|
def today():
|
|
import time
|
|
local = time.localtime(time.time())
|
|
return Date(local[1], local[2], local[0])
|
|
|
|
class DateTestError(Exception):
|
|
pass
|
|
|
|
def test(firstyear, lastyear):
|
|
a = Date(9,30,1913)
|
|
b = Date(9,30,1914)
|
|
if repr(a) != 'Tue 30 Sep 1913':
|
|
raise DateTestError('__repr__ failure')
|
|
if (not a < b) or a == b or a > b or b != b:
|
|
raise DateTestError('__cmp__ failure')
|
|
if a+365 != b or 365+a != b:
|
|
raise DateTestError('__add__ failure')
|
|
if b-a != 365 or b-365 != a:
|
|
raise DateTestError('__sub__ failure')
|
|
try:
|
|
x = 1 - a
|
|
raise DateTestError('int-date should have failed')
|
|
except TypeError:
|
|
pass
|
|
try:
|
|
x = a + b
|
|
raise DateTestError('date+date should have failed')
|
|
except TypeError:
|
|
pass
|
|
if a.weekday() != 'Tuesday':
|
|
raise DateTestError('weekday() failure')
|
|
if max(a,b) is not b or min(a,b) is not a:
|
|
raise DateTestError('min/max failure')
|
|
d = {a-1:b, b:a+1}
|
|
if d[b-366] != b or d[a+(b-a)] != Date(10,1,1913):
|
|
raise DateTestError('dictionary failure')
|
|
|
|
# verify date<->number conversions for first and last days for
|
|
# all years in firstyear .. lastyear
|
|
|
|
lord = _days_before_year(firstyear)
|
|
y = firstyear
|
|
while y <= lastyear:
|
|
ford = lord + 1
|
|
lord = ford + _days_in_year(y) - 1
|
|
fd, ld = Date(1,1,y), Date(12,31,y)
|
|
if (fd.ord,ld.ord) != (ford,lord):
|
|
raise DateTestError('date->num failed', y)
|
|
fd, ld = _num2date(ford), _num2date(lord)
|
|
if (1,1,y,12,31,y) != \
|
|
(fd.month,fd.day,fd.year,ld.month,ld.day,ld.year):
|
|
raise DateTestError('num->date failed', y)
|
|
y = y + 1
|
|
|
|
if __name__ == '__main__':
|
|
test(1850, 2150)
|