import datetime
my_date = datetime.date.today() # if date is 01/01/2018
year, week_num, day_of_week = my_date.isocalendar()
print("Week #" + str(week_num) + " of year " + str(year))
#OUTPUT
#Week #1 of year 2018
import datetime
from dateutil.relativedelta import relativedelta
week = 25
year = 2021
date = datetime.date(year, 1, 1) + relativedelta(weeks=+week)
print(date)