Looking for days between two given dates in a string format

Question

I do have data like this: [a, startdate, enddate]

a_list = [ ['a', '2021-02-22', '2021-02-25'] ]

and would like to get the days between those two dates to be like [a, startdate, enddate, days between those dates]

a_list = [ ['a', '2021-02-22', '2021-02-25', 3] ]

How do I approach this problem? Thanks in advance!

Answer 1

Working out of the box solution:

from datetime import datetime

a_list = [ ['a', '2021-02-22', '2021-02-25'] ]
res = []

for el in a_list:
    d1 = datetime.strptime(el[1], '%Y-%M-%d')
    d2 = datetime.strptime(el[2], '%Y-%M-%d')
    res.append(el + [(d2-d1).days])

res
>>> [['a', '2021-02-22', '2021-02-25', 3]]

Answer 2

1. Turn your strings into datetime.date types

   import datetime
   
   a_dt = datetime.date.strptime(a_list[0][1],'%Y-%m-%d')     
   b_dt = datetime.date.strptime(a_list[0][2],'%Y-%m-%d')
   

2. Compute the datetime.timedelta difference between them

   days_between = (b_dt - a_dt).days # Assuming b_dt is after a_dt for +ve days
   

3. Append the result to your list.

   a_list[0].append( days_between )
   

Answer 3

This is the easiest way to reach your goal.

from datetime import datetime

a_list = [ ['a', '2021-02-22', '2021-02-25'] ]
start_date = datetime.strptime(a_list[0][1], '%Y-%M-%d')
end_date = datetime.strptime(a_list[0][2], '%Y-%M-%d')
days = (end_date-start_date).days
a_list[0].append(days)
print(a_list)