>>> import datetime
>>> from datetime import timedelta
>>> now=datetime.datetime.now()
>>> today=now
#今天
>>> now
datetime.datetime(2019, 10, 9, 17, 25, 9, 459542)
#格式化今天
>>> now.strftime('%Y-%m-%d %H:%M:%S')
'2019-10-09 17:25:09'
#昨天
>>> yesterday=now-timedelta(days=1)
>>> yesterday
datetime.datetime(2019, 10, 8, 17, 25, 9, 459542)
#格式化昨天
>>> yesterday.strftime('%Y-%m-%d %H:%M:%S')
'2019-10-08 17:25:09'