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git-svn-id: http://svn.python.org/projects/python/trunk@3545 6015fed2-1504-0410-9fe1-9d1591cc4771
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‎Demo/classes/Dates.py‎

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# Class Date supplies date objects that support date arithmetic.
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#
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# Date(month,day,year) returns a Date object. An instance prints as,
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# e.g., 'Mon 16 Aug 1993'.
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#
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# Addition, subtraction, comparison operators, min, max, and sorting
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# all work as expected for date objects: int+date or date+int returns
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# the date `int' days from `date'; date+date raises an exception;
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# date-int returns the date `int' days before `date'; date2-date1 returns
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# an integer, the number of days from date1 to date2; int-date raises an
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# exception; date1 < date2 is true iff date1 occurs before date2 (&
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# similarly for other comparisons); min(date1,date2) is the earlier of
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# the two dates and max(date1,date2) the later; and date objects can be
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# used as dictionary keys.
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#
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# Date objects support one visible method, date.weekday(). This returns
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# the day of the week the date falls on, as a string.
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#
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# Date objects also have 4 (conceptually) read-only data attributes:
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# .month in 1..12
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# .day in 1..31
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# .year int or long int
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# .ord the ordinal of the date relative to an arbitrary staring point
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#
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# The Dates module also supplies function today(), which returns the
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# current date as a date object.
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#
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# Those entranced by calendar trivia will be disappointed, as no attempt
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# has been made to accommodate the Julian (etc) system. On the other
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# hand, at least this package knows that 2000 is a leap year but 2100
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# isn't, and works fine for years with a hundred decimal digits <wink>.
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# Tim Peters tim@ksr.com
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# not speaking for Kendall Square Research Corp
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_MONTH_NAMES = [ 'January', 'February', 'March', 'April', 'May',
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'June', 'July', 'August', 'September', 'October',
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'November', 'December' ]
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_DAY_NAMES = [ 'Friday', 'Saturday', 'Sunday', 'Monday',
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'Tuesday', 'Wednesday', 'Thursday' ]
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_DAYS_IN_MONTH = [ 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 ]
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_DAYS_BEFORE_MONTH = []
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dbm = 0
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for dim in _DAYS_IN_MONTH:
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_DAYS_BEFORE_MONTH.append(dbm)
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dbm = dbm + dim
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del dbm, dim
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_INT_TYPES = type(1), type(1L)
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def _is_leap( year ): # 1 if leap year, else 0
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if year % 4 != 0: return 0
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if year % 400 == 0: return 1
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return year % 100 != 0
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def _days_in_year( year ): # number of days in year
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return 365 + _is_leap(year)
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def _days_before_year( year ): # number of days before year
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return year*365L + (year+3)/4 - (year+99)/100 + (year+399)/400
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def _days_in_month( month, year ): # number of days in month of year
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if month == 2 and _is_leap(year): return 29
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return _DAYS_IN_MONTH[month-1]
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def _days_before_month( month, year ): # number of days in year before month
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return _DAYS_BEFORE_MONTH[month-1] + (month > 2 and _is_leap(year))
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def _date2num( date ): # compute ordinal of date.month,day,year
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return _days_before_year( date.year ) + \
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_days_before_month( date.month, date.year ) + \
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date.day
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_DI400Y = _days_before_year( 400 ) # number of days in 400 years
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def _num2date( n ): # return date with ordinal n
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if type(n) not in _INT_TYPES:
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raise TypeError, 'argument must be integer: ' + `type(n)`
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ans = Date(1,1,1) # arguments irrelevant; just getting a Date obj
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ans.ord = n
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n400 = (n-1)/_DI400Y # # of 400-year blocks preceding
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year, n = 400 * n400, n - _DI400Y * n400
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more = n / 365
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dby = _days_before_year( more )
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if dby >= n:
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more = more - 1
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dby = dby - _days_in_year( more )
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year, n = year + more, int(n - dby)
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try: year = int(year) # chop to int, if it fits
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except ValueError: pass
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month = min( n/29 + 1, 12 )
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dbm = _days_before_month( month, year )
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if dbm >= n:
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month = month - 1
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dbm = dbm - _days_in_month( month, year )
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ans.month, ans.day, ans.year = month, n-dbm, year
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return ans
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def _num2day( n ): # return weekday name of day with ordinal n
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return _DAY_NAMES[ int(n % 7) ]
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class Date:
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def __init__( self, month, day, year ):
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if not 1 <= month <= 12:
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raise ValueError, 'month must be in 1..12: ' + `month`
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dim = _days_in_month( month, year )
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if not 1 <= day <= dim:
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raise ValueError, 'day must be in 1..' + `dim` + ': ' + `day`
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self.month, self.day, self.year = month, day, year
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self.ord = _date2num( self )
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def __cmp__( self, other ):
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return cmp( self.ord, other.ord )
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# define a hash function so dates can be used as dictionary keys
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def __hash__( self ):
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return hash( self.ord )
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# print as, e.g., Mon 16 Aug 1993
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def __repr__( self ):
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return '%.3s %2d %.3s ' % (
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self.weekday(),
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self.day,
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_MONTH_NAMES[self.month-1] ) + `self.year`
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# automatic coercion is a pain for date arithmetic, since e.g.
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# date-date and date-int mean different things. So, in order to
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# sneak integers past Python's coercion rules without losing the info
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# that they're really integers (& not dates!), integers are disguised
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# as instances of the derived class _DisguisedInt. That this works
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# relies on undocumented behavior of Python's coercion rules.
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def __coerce__( self, other ):
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if type(other) in _INT_TYPES:
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return self, _DisguisedInt(other)
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# if another Date, fine
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if type(other) is type(self) and other.__class__ is Date:
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return self, other
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# Python coerces int+date, but not date+int; in the former case,
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# _DisguisedInt.__add__ handles it, so we only need to do
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# date+int here
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def __add__( self, n ):
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if type(n) not in _INT_TYPES:
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raise TypeError, 'can\'t add ' + `type(n)` + ' to date'
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return _num2date( self.ord + n )
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# Python coerces all of int-date, date-int and date-date; the first
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# case winds up in _DisguisedInt.__sub__, leaving the latter two
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# for us
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def __sub__( self, other ):
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if other.__class__ is _DisguisedInt: # date-int
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return _num2date( self.ord - other.ord )
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else:
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return self.ord - other.ord # date-date
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def weekday( self ):
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return _num2day( self.ord )
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# see comments before Date.__add__
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class _DisguisedInt( Date ):
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def __init__( self, n ):
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self.ord = n
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# handle int+date
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def __add__( self, other ):
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return other.__add__( self.ord )
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# complain about int-date
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def __sub__( self, other ):
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raise TypeError, 'Can\'t subtract date from integer'
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def today():
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import time
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local = time.localtime(time.time())
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return Date( local[1], local[2], local[0] )
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DateTestError = 'DateTestError'
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def test( firstyear, lastyear ):
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a = Date(9,30,1913)
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b = Date(9,30,1914)
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if `a` != 'Tue 30 Sep 1913':
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raise DateTestError, '__repr__ failure'
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if (not a < b) or a == b or a > b or b != b or \
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a != 698982 or 698982 != a or \
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(not a > 5) or (not 5 < a):
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raise DateTestError, '__cmp__ failure'
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if a+365 != b or 365+a != b:
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raise DateTestError, '__add__ failure'
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if b-a != 365 or b-365 != a:
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raise DateTestError, '__sub__ failure'
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try:
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x = 1 - a
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raise DateTestError, 'int-date should have failed'
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except TypeError:
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pass
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try:
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x = a + b
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raise DateTestError, 'date+date should have failed'
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except TypeError:
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pass
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if a.weekday() != 'Tuesday':
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raise DateTestError, 'weekday() failure'
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if max(a,b) is not b or min(a,b) is not a:
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raise DateTestError, 'min/max failure'
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d = {a-1:b, b:a+1}
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if d[b-366] != b or d[a+(b-a)] != Date(10,1,1913):
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raise DateTestError, 'dictionary failure'
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# verify date<->number conversions for first and last days for
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# all years in firstyear .. lastyear
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lord = _days_before_year( firstyear )
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y = firstyear
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while y <= lastyear:
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ford = lord + 1
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lord = ford + _days_in_year(y) - 1
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fd, ld = Date(1,1,y), Date(12,31,y)
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if (fd.ord,ld.ord) != (ford,lord):
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raise DateTestError, ('date->num failed', y)
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fd, ld = _num2date(ford), _num2date(lord)
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if (1,1,y,12,31,y) != \
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(fd.month,fd.day,fd.year,ld.month,ld.day,ld.year):
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raise DateTestError, ('num->date failed', y)
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y = y + 1

‎Demo/classes/Rev.py‎

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# A class which presents the reverse of a sequence without duplicating it.
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# From: "Steven D. Majewski" <sdm7g@elvis.med.virginia.edu>
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# It works on mutable or inmutable sequences.
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#
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# >>> for c in Rev( 'Hello World!' ) : sys.stdout.write( c )
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# ... else: sys.stdout.write( '\n' )
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# ...
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# !dlroW olleH
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#
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# The .forw is so you can use anonymous sequences in init, and still
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# keep a reference the forward sequence. )
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# If you give it a non-anonymous mutable sequence, the reverse sequence
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# will track the updated values. ( but not reassignment! - another
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# good reason to use anonymous values in creating the sequence to avoid
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# confusion. Maybe it should be change to copy input sequence to break
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# the connection completely ? )
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#
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# >>> nnn = range( 0, 3 )
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# >>> rnn = Rev( nnn )
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# >>> for n in rnn: print n
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# ...
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# 2
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# 1
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# 0
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# >>> for n in range( 4, 6 ): nnn.append( n ) # update nnn
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# ...
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# >>> for n in rnn: print n # prints reversed updated values
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# ...
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# 5
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# 4
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# 2
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# 1
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# 0
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# >>> nnn = nnn[1:-1]
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# >>> nnn
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# [1, 2, 4]
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# >>> for n in rnn: print n # prints reversed values of old nnn
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# ...
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# 5
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# 4
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# 2
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# 1
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# 0
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# >>>
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#
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# WH = Rev( 'Hello World!' )
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# print WH.forw, WH.back
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# nnn = Rev( range( 1, 10 ) )
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# print nnn.forw
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# print nnn
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#
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# produces output:
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#
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# Hello World! !dlroW olleH
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# [1, 2, 3, 4, 5, 6, 7, 8, 9]
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# [9, 8, 7, 6, 5, 4, 3, 2, 1]
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#
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# >>>rrr = Rev( nnn )
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# >>>rrr
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# <1, 2, 3, 4, 5, 6, 7, 8, 9>
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from string import joinfields
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class Rev:
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def __init__( self, seq ):
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self.forw = seq
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self.back = self
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def __len__( self ):
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return len( self.forw )
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def __getitem__( self, j ):
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return self.forw[ -( j + 1 ) ]
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def __repr__( self ):
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seq = self.forw
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if type(seq) == type( [] ) :
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wrap = '[]'
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sep = ', '
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elif type(seq) == type( () ) :
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wrap = '()'
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sep = ', '
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elif type(seq) == type( '' ) :
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wrap = ''
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sep = ''
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else:
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wrap = '<>'
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sep = ', '
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outstrs = []
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for item in self.back :
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outstrs.append( str( item ) )
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return wrap[:1] + joinfields( outstrs, sep ) + wrap[-1:]

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