dateeee

from datetime import date, timedelta, datetime
a = "20210201"
date = datetime.strptime(a, '%Y%m%d')

last_day_of_prev_month = date.replace(day=1) - timedelta(days=1)
start_day_of_prev_month = date.today().replace(day=1) - timedelta(days=last_day_of_prev_month.day)
b = start_day_of_prev_month.strftime('%Y%m%d')
# For printing results
print(a)
print(b)