python imprime el final del mes pasado

import datetime
# 当前时间
today = datetime.datetime.now()
# 当月月初
first = datetime.date(today.year,today.month,1)
delta = datetime.timedelta(days=1)
# 月初减一天即为上月月底
newtime = first - delta
print(newtime.strftime("%Y%m%d"))