# Simple date class

import re

patt = "[/.,; ]"

class Dates(object):

monthDict = dict(zip(range(1,13),['January', 'February', 'March', 'April', \

'May', 'June', 'July', 'August', 'September', \

'October', 'November', 'December']))

daysList1 = [31,28,31,30,31,30,31,31,30,31,30,31]

daysList2 = [31,29,31,30,31,30,31,31,30,31,30,31]

def __init__(self, dateStr):

# dateStr is in the format month/day/year (xx/xx/xxxx) or month.day.year

self.dateStr = dateStr

try:

self.month, self.day, self.year = [int(s) for s in re.split(patt, dateStr)]

except:

raise ValueError, "Invalid date format"

self.month_str = self.monthStr()

self.day_num = self.dayNo()

def isLeap(self, yr):

if not yr % 4:

return 1

return 0

def daysList(self, year):

return [self.daysList1, self.daysList2][self.isLeap(year)]

def monthStr(self):

# return the text representation of the month number

try:

return self.monthDict[self.month]

except KeyError:

raise ValueError, "Invalid month number"

def dayNo(self):

# return the day number in the year

if self.day < 1 or self.day > self.daysList(self.year)[self.month-1]:

raise ValueError, "Invalid day number"

return sum(self.daysList(self.year)[:self.month-1]) + self.day

def monthDayYr(self, day_num):

# return a tuple of month, day, year given a day number

# day number is with respect to the year of the instance

idx = 0

year = self.year

while day_num < 1:

day_num += sum(self.daysList(year))

year -= 1

while True:

if day_num <= self.daysList(year)[idx]:

return idx+1, day_num, year

day_num -= self.daysList(year)[idx]

idx += 1

if idx == 12:

idx = 0

year += 1

def nextDay(self):

return self+1

def preDay(self):

return self-1

def daysToZero(self):

# calculate the number of days with respect to year 0

if self.year < 0:

yrList = xrange(self.year, 0)

days = -self.dayNo()

else:

yrList = xrange(0, self.year)

days = self.dayNo()

return days + sum([sum(self.daysList(yr)) for yr in yrList])

def diff(self, other):

year_diff = self.year - other.year

if year_diff < 0:

yrList = xrange(self.year, other.year)

days = self.dayNo() - other.dayNo()

else:

yrList = xrange(other.year, self.year)

days = other.dayNo() - self.dayNo()

return days - sum([sum(self.daysList(yr)) for yr in yrList])

def __add__(self, days):

return Dates('/'.join([str(item) for item in self.monthDayYr(self.dayNo() + days)]))

def __sub__(self, days):

# days can be an int or a Dates() object

# return a Dates() object, or the number of days difference

if isinstance(days, int):

return Dates('/'.join([str(item) for item in self.monthDayYr(self.dayNo() - days)]))

# days is an instance of Dates if not an int

return self.daysToZero()-days.daysToZero()

def __str__(self):

return "%s %d, %d" % (self.month_str, self.day, self.year)

if __name__ == '__main__':

a = Dates('6/8/2007')

print a

print a.nextDay()

print a.preDay()

b = a+90039

print b

c = a-4665

print c

d = Dates('12/31/2000')

print d.dayNo()

f = Dates('2.29.2000')

print f

print f.isLeap(f.year)

print f.daysList(f.year)

print f-d

print f.diff(d)

print d.diff(f)

print a-b

print a.diff(b)

print b-a

print b.diff(a)

'''

>>> June 8, 2007

June 9, 2007

June 7, 2007

December 12, 2253

August 30, 1994

366

February 29, 2000

1

[31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

-306

-306

306

-90039

-90039

90039

90039

>>> >>> a = Dates('12/31/2007')

>>> b = Dates('12/31/2006')

>>> c = Dates('12/31/2005')

>>> d = Dates('12/31/2004')

>>> e = Dates('12/31/2008')

>>> f = Dates('12/31/2003')

>>> a-b

365

>>> e-a

366

>>> e-f

1827

>>> 1827%365

2

>>> a-e

-366

>>> f-e

-1827

>>>

'''