python学习===打印时间
>>> import time
>>> print(time.time())
1501749158.9849465
>>> print(time.localtime())
time.struct_time(tm_year=2017, tm_mon=8, tm_mday=3, tm_hour=16, tm_min=33, tm_sec=22, tm_wday=3, tm_yday=215, tm_isdst=0)
>>> print(time.asctime())
Thu Aug 3 16:34:08 2017
>>> print(time.strftime('%Y-%m-%d %H:%M:%S',time.localtime()))
2017-08-03 16:36:28
>>> import datetime
>>> print(datetime.date.today())
2017-08-03
>>> print(datetime.date(1992, 3 , 11))
1992-03-11