python计算当月第一天，最后一天

from dateutil.relativedelta import relativedelta
import  d服务器托管网atetime
today = datetime.datetime.today()
# 第一天
first_day=(relativedelta() + today).replace(day=1)
print (first_day)
# 最后一天
last_day = (relativedelta(months=1) + today).replace(day=1) - relativedelta(days=1)
print  ( last_day)
if today==first_day:
    print ("第一天")
if today==last_day:
    print ("最后一天")