'''
Chronological file backup example
'''

import datetime
import time

#to generate a date:
#x=datetime.datetime.now().strftime('%Y-%m-%d')

#Sample dates
DATES = ['2021-01-07', '2021-02-14', '2021-06-22',
         '2021-04-14', '2021-03-19', '2021-07-11', '2021-05-14']

#sample file names
FNAMES = ['SP_dryad_production.sqlite3.'+ x for x in DATES]

#Note: min max etc work on dictionary keys
#datetime.datetime(*(time.strptime(y, '%Y-%m-%d %H:%M:%S')[0:6]))#painful
#see https://python.readthedocs.io/en/latest/library/datetime.html

FNAME_D={datetime.datetime(
    *(time.strptime(dat[-10:],'%Y-%m-%d')[0:6])): dat
	 for dat in FNAMES}
TIMES = list(FNAME_D)
TIMES.sort()
#There can be only 3
for fil in TIMES[3:]:
    print(f'os.remove({FNAME_D[fil]})')
    del FNAMES[FNAMES.index(FNAME_D[fil])]
print(FNAMES)