python datetime模块

该模块的时间有限时限：1 - 9999

dir(datetime) 

 from datetime import datetime, timedelta, timezone

 dt = datetime.now()
 t = dt.timestamp()

 dt1 = datetime.fromtimestamp(t)

 utc_dt = datetime.utcfromtimestamp(t)

 tz_utc_8 = timezone(timedelta(hours=8))
 utc_dt1 = dt.replace(tzinfo=tz_utc_8)

 str1 = dt.strftime("%Y-%m-%d %X")
 str2 = dt.ctime()

 dt2 = datetime.strptime('2016-11-27', "%Y-%m-%d")

 st = dt.timetuple()

 dt3 = dt + timedelta(days=2, hours=1)

练习：

（1）现在时间
（2）指定时间
（3）闰年判定
（4）今年第几天
（5）今天第几周
（6）程序运行时间
（7）判定星期几
（8）时间日期比较

 "（1）现在时间"
 from datetime import datetime

 now1 = datetime.now()
 now2 = datetime.today()
 print(now1)
 print(now2)

 "（2）指定时间"
 dt = datetime(2016, 12, 3, 21, 17)
 print(dt)

 "（3）闰年判定"
 import calendar

 if calendar.isleap(2016):
     print("leap year")

 "（4）今年第几天"
 import time

 print(time.localtime().tm_yday)
 print(time.strftime("%j"))

 "（5）今天第几周"
 print(time.strftime("%W"))

 "（6）程序运行时间"
 t1 = time.time()
 t2 = time.time()
 print("run time: ", t2 - t1)

 t1 = time.clock()
 t2 = time.clock()
 print("{}".format(t2))

 "（7）判定星期几"
 "0-6"
 print(datetime.now().weekday())

 "（8）时间日期比较"

 dt1 = datetime(2016, 12, 3)
 dt2 = datetime(2016, 12, 4)
 print(dt1 > dt2)
 print(dt1 == dt2)
 print(dt1 < dt2)
 print(dt1 is dt2)
 print(dt1 is not dt2)