Python获取当前时间的前(后)N天，前(后)N周，前（后）N月

获取当前时间的前（后）N天

def get_days_before_today(n=0):
    '''''
    date format = "YYYY-MM-DD HH:MM:SS"
    '''
    now = datetime.datetime.now()
    if(n<0):
	return datetime.datetime(now.year, now.month, now.day, now.hour, now.minute, now.second)
    else:
	n_days_before = now - timedelta(days=n)
    return datetime.datetime(n_days_before.year, n_days_before.month, n_days_before.day, n_days_before.hour, n_days_before.minute, n_days_before.second)

获取当前时间的前（后）N周

def get_weeks_before_tody(n=0):
    '''''
    date format = "YYYY-MM-DD HH:MM:SS"
    '''
    now = datetime.datetime.now()
    if(n<0):
	return datetime.datetime(now.year, now.month, now.day, now.hour, now.minute, now.second)
    else:
	n_days_before = now - timedelta(days=n*7)
    return datetime.datetime(n_days_before.year, n_days_before.month, n_days_before.day, n_days_before.hour, n_days_before.minute, n_days_before.second)

获得当前时间的前（后）N月

def get_now_time():
	now = datetime.datetime.now()
    thisyear = int(now.year)
    thismon = int(now.month)
    thisday = int(now.day)
    thishour = int(now.hour)
    thisminute = int(now.minute)
    thissecond = int(now.second)
    return thisyear, thismon, thisday, thishour, thisminute, thissecond

def get_year_and_month(n=0): 
    ''''' 
    get the year,month,days from today 
    befor or after n months 
    '''
    now = datetime.datetime.now()
    thisyear, thismon, thisday, thishour, thisminute, thissecond = get_now_time()
    totalmon = thismon+n

    if(n>=0): 
        if(totalmon<=12): 
            days = str(get_days_of_month(thisyear,totalmon)) 
            totalmon = add_zero(totalmon) 
            return (thisyear, totalmon, days, thishour, thisminute, thissecond, thisday) 
        else: 
            i = totalmon/12 
            j = totalmon%12 
            if(j==0): 
                i-=1 
                j=12 
            thisyear += i 
            days = str(get_days_of_month(thisyear,j)) 
            j = add_zero(j) 
            return (str(thisyear),str(j),days, thishour,thisminute, thissecond, thisday) 
    else: 
        if((totalmon>0) and (totalmon<12)): 
            days = str(get_days_of_month(thisyear,totalmon)) 
            totalmon = add_zero(totalmon) 
            return (thisyear,totalmon,days, thishour, thisminute, thissecond, thisday) 
        else: 
            i = totalmon/12 
            j = totalmon%12 
            if(j==0): 
                i-=1 
                j=12 
            thisyear +=i 
            days = str(get_days_of_month(thisyear,j)) 
            j = add_zero(j) 
            return (str(thisyear),str(j),days, thishour, thisminute, thissecond, thisday) 

def get_days_of_month(year,mon): 
    return calendar.monthrange(year, mon)[1] 

def add_zero(n): 
    ''''' 
    add 0 before 0-9 
    return 01-09 
    ''' 
    nabs = abs(int(n)) 
    if(nabs<10): 
        return "0"+str(nabs) 
    else: 
        return nabs

def get_today_months(n=0): 
    year,mon,d, hour, minute,second, day = get_year_and_month(n)
    arr = (year,mon,d, hour, minute,second, day)
    print arr
    if(int(day)