timedate如何查看当前时间并去除毫秒

import datetime

dt = datetime.datetime.strptime(str(datetime.datetime.now().replace(microsecond=0)),'%Y-%m-%d %H:%M:%S')
#datetime.datetime.now()显示当前时间.replace(microsecond=0)保留0位毫秒

a = dt + datetime.timedelta(days=3)  #3天后
b = dt + datetime.timedelta(days=-7) #3天前

print(b)