How to filter out strings from a list of strings with dates?

How to filter out this list, so that we are left with only a list of strings that are in yyyy-mm-dd format?

2021-11-11
2021-10-01
some_folder
some_other_folder

so that we end up with a list like so:

2021-11-11
2021-10-01

Also what if the list has a prefix?

root/2021-11-11
root/2021-10-01
user/some_folder
root/some_other_folder

and we wanted to end up with:

root/2021-11-11
root/2021-10-01

>Solution :

I would let datetime module handle that for me using strptime. If it is not in '%Y-%m-%d' format, it raises ValueError :

import datetime

lst = ['2021-11-11', '2021-10-01', 'some_folder', 'some_other_folder',
       'root/2021-11-11', 'root/2021-10-01',
       'user/some_folder', 'root/some_other_folder']


def filter(s):
    last_part = s.rsplit('/', maxsplit=1)[-1]
    try:
        datetime.datetime.strptime(last_part, '%Y-%m-%d')
        return True
    except ValueError:
        return False


print([i for i in lst if filter(i)])

output :

['2021-11-11', '2021-10-01', 'root/2021-11-11', 'root/2021-10-01']