Python时间系统

Python的time和datetime模块提供了时间日期工具, python中的时间有4种表示方式:

• datetime obj

• time obj/tuple

• posix timestamp

• timestring

datetime#

获得当前时间:

>>> import datetime
>>> datetime.datetime.now()
datetime.datetime(2016, 8, 21, 16, 21, 51, 631199)

创建datetime对象:

>>> d = datetime.datetime(year=2016, month=1, day=1, hour=12, minute=0, second=0)
>>> d
datetime.datetime(2016, 1, 1, 12, 0)
>>> d.year
2016

datetime是不可变对象, 若要修改时间需要建立新的datetime对象.

但是datetime可以相减,比较或加减timedelta:

>>> datetime.datetime.now() - d
datetime.timedelta(233, 16611, 887646)
>>> datetime.datetime.now() < d
False
>>> datetime.datetime.now() + datetime.timedelta(1)
datetime.datetime(2016, 8, 22, 16, 38, 30, 306021)

转换为time tuple:

>>> d.timetuple()
time.struct_time(tm_year=2016, tm_mon=1, tm_mday=1, tm_hour=12, tm_min=0, tm_sec=0, tm_wday=4, tm_yday=1, tm_isdst=-1)

通过time tuple转换为时间戳:

>>> time.mktime(datetime.datetime.now().timetuple())
1471777789.0

格式化为时间字符串:

>>> datetime.datetime.now().strftime('%Y-%m-%d %H:%M:%S %f')
'2016-08-21 16:46:20 634139'

time#

获得当前时间:

>>> import time
>>> time.localtime()
time.struct_time(tm_year=2016, tm_mon=8, tm_mday=21, tm_hour=16, tm_min=48, tm_sec=24, tm_wday=6, tm_yday=234, tm_isdst=0)

转换为datetime:

>>> datetime.datetime(*time.localtime()[0:6])
datetime.datetime(2016, 8, 21, 16, 56, 16)

格式化为时间字符串:

>>> time.strftime('%Y-%m-%d %H:%M:%S', time.localtime())
'2016-08-21 16:55:01'

转换为时间戳:

>>> time.mktime(time.localtime())
1471770256.0

时间戳#

UNIX时间戳定义为1970-1-1 00:00:00开始的秒数, 获得当前时间戳:

>>> import time
>>> time.time()
1471777412.3293073

转换为datetime:

>>> datetime.datetime.fromtimestamp(time.time())
datetime.datetime(2016, 8, 21, 19, 8, 22, 719951)

转换为timetuple:

>>> time.localtime(time.time())
time.struct_time(tm_year=2016, tm_mon=8, tm_mday=21, tm_hour=19, tm_min=13, tm_sec=41, tm_wday=6, tm_yday=234, tm_isdst=0)