如何通过在python中仅输入一年中的某一天获得相关的月份和日期

Question

I'm developing a phonebook application from python as a mini project in which I'm having the requirement to store the NIC number of a person and then display his/her gender, DOB and age. I have to derive these 3 information and I'm able to derive the gender, but I don't know how to derive the DOB - only the birth year because the NIC number's first 2 digits represent the year of birth.

In a NIC number, the 3rd three digits are the day of year :- from 001 to 366. I can seperate those 3 digits to another variable as well, but how do I derive the month and the date of month which it refers to?

For example :

derivedYear = 1996
dayOfYear = 032

finalDOB = "1996.02.01"
print finalDOB

I want to know how to calculate the finalDOB value. I'm using python 2.7.6

Answer 1

You can use timedelta() . It can take days as an argument, and when added to a date, will shift it by that amount.

import datetime

year = 1996
days = 32

date = datetime.date(year, 1, 1) #Will give 1996-01-01
delta = datetime.timedelta(days - 1) #str(delta) will be '31 days, 0:00:00'
newdate = date + delta

>>> str(newdate) 
>>> 1996-02-01

or

>>> newdate.strftime('%Y.%m.%d')
>>> '1996.02.01'

Answer 2

You can use %j format for day of year in datetime.datetime.strptime() , to get the corresponding datetime object . Example -

>>> derivedYear = 1996
>>> dayOfYear = 32
>>> import datetime
>>> d = datetime.datetime.strptime('{} {}'.format(dayOfYear, derivedYear),'%j %Y')
>>> d
datetime.datetime(1996, 2, 1, 0, 0)

Then you can use the .day and .month attribute of the datetime object to get the corresponding day and month. Example -

>>> d.day
1
>>> d.month
2

If you want the result in format - YYYY.MM.DD - you can use strftime() and supply the format to it. Example -

>>> d.strftime('%Y.%m.%d')
'1996.02.01'

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Also, please note, you should not define your dayOfYear with a leading 0 , as that would make the literal an octal number, which would not be what you want.