Convert Year/Month/Day to Day of Year in Python

Question

I'm using the Python "datetime" module, i.e.:

>>> import datetime
>>> today = datetime.datetime.now()
>>> print today
2009-03-06 13:24:58.857946

and I would like to compute the day of year that is sensitive of leap years. e.g. oday (March 6, 2009) is the 65th day of 2009. Here's web-based DateTime calculator.

Anyway, I see a two options:

1. Create a number_of_days_in_month array = [31, 28, ...], decide if it's a leap year, manually sum up the days

2. Use datetime.timedelta to make a guess & then binary search for the correct day of year:

.

>>> import datetime
>>> YEAR = 2009
>>> DAY_OF_YEAR = 62
>>> d = datetime.date(YEAR, 1, 1) + datetime.timedelta(DAY_OF_YEAR - 1)

These both feel pretty clunky & I have a gut feeling that there's a more "Pythonic" way of calculating day of year. Any ideas/suggestions?

Answer 1

Couldn't you use strftime?

>>> import datetime
>>> today = datetime.datetime.now()
>>> print today
2009-03-06 15:37:02.484000
>>> today.strftime('%j')
'065'

Edit

As noted in the comments, if you wish to do comparisons or calculations with this number, you would have to convert it to int() because strftime() returns a string. If that is the case, you are better off using DzinX's answer.

Answer 2

Just subtract january 1 from the date:

import datetime
today = datetime.datetime.now()
day_of_year = (today - datetime.datetime(today.year, 1, 1)).days + 1

Answer 3

There is a very simple solution:

day_of_year = datetime.now().timetuple().tm_yday