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)