Convert Calendar Date To Julian Date - Python

I am trying to convert calendar date like so: '2018-08-07' to julian calendar day like so '219'. I have tried for a long time and seem to run out of ideas. The julian day calendar

Solution 1:

You can use strftime for this (see this for a description of directives to use):

jul = df.strftime('%j')
>>> jul
'219'

Solution 2:

def date_2_julian_string (date):
    return str(date.strftime('%y')) + date.strftime('%j')