python获取当前日期前后N天或N月的日期

#!/usr/bin/python
'''
Filename: "utildate.py"
author:   "zhangsong"
date  :   "2009-03-24"
version:  "1.00"
'''
from time import strftime, localtime
from datetime import timedelta, date
import calendar
year = strftime("%Y",localtime())
mon  = strftime("%m",localtime())
day  = strftime("%d",localtime())
hour = strftime("%H",localtime())
min  = strftime("%M",localtime())
sec  = strftime("%S",localtime())

def today():
'''
get today,date format="YYYY-MM-DD"
'''
return date.today()
def todaystr():
'''
get date string
date format="YYYYMMDD"
'''
return year+mon+day
def datetime():
'''
get datetime,format="YYYY-MM-DD HH:MM:SS"
'''
return strftime("%Y-%m-%d %H:%M:%S",localtime())
def datetimestr():
'''
get datetime string
date format="YYYYMMDDHHMMSS"
'''
return year+mon+day+hour+min+sec
def getdayofday(n=0):
'''
if n>=0,date is larger than today
if n<0,date is less than today
date format = "YYYY-MM-DD"
'''
if(n<0):
n = abs(n)
return date.today()-timedelta(days=n)
else:
return date.today()+timedelta(days=n)
def getdaysofmonth(year,mon):
'''
get days of month
'''
return calendar.monthrange(year, mon)[1]
def getfirstdayofmonth(year,mon):
'''
get the first day of month
date format = "YYYY-MM-DD"
'''
days="01"
if(int(mon)<10):
mon = "0"+str(int(mon))
arr = (year,mon,days)
return "-".join("%s" %i for i in arr)
def getlastdayofmonth(year,mon):
'''
get the last day of month
date format = "YYYY-MM-DD"
'''
days=calendar.monthrange(year, mon)[1]
mon = addzero(mon)
arr = (year,mon,days)
return "-".join("%s" %i for i in arr)
def get_firstday_month(n=0):
'''
get the first day of month from today
n is how many months
'''
(y,m,d) = getyearandmonth(n)
d = "01"
arr = (y,m,d)
return "-".join("%s" %i for i in arr)
def get_lastday_month(n=0):
'''
get the last day of month from today
n is how many months
'''
return "-".join("%s" %i for i in getyearandmonth(n))

def get_today_month(n=0):
'''
get last or next month's today
n is how many months
date format = "YYYY-MM-DD"
'''
(y,m,d) = getyearandmonth(n)
arr=(y,m,d)
if(int(day)<int(d)):
arr = (y,m,day)
return "-".join("%s" %i for i in arr)
def getyearandmonth(n=0):
'''
get the year,month,days from today
befor or after n months
'''
thisyear = int(year)
thismon = int(mon)
totalmon = thismon+n
if(n>=0):
if(totalmon<=12):
days = str(getdaysofmonth(thisyear,totalmon))
totalmon = addzero(totalmon)
return (year,totalmon,days)
else:
i = totalmon/12
j = totalmon%12
if(j==0):
i-=1
j=12
thisyear += i
days = str(getdaysofmonth(thisyear,j))
j = addzero(j)
return (str(thisyear),str(j),days)
else:
if((totalmon>0) and (totalmon<12)):
days = str(getdaysofmonth(thisyear,totalmon))
totalmon = addzero(totalmon)
return (year,totalmon,days)
else:
i = totalmon/12
j = totalmon%12
if(j==0):
i-=1
j=12
thisyear +=i
days = str(getdaysofmonth(thisyear,j))
j = addzero(j)
return (str(thisyear),str(j),days)
def addzero(n):
'''
add 0 before 0-9
return 01-09
'''
nabs = abs(int(n))
if(nabs<10):
return "0"+str(nabs)
else:
return nabs
#print today()
#print addzero(10)
print get_today_month(-1)
print get_lastday_month(3)
print get_firstday_month(3)