Python的time模块详解

python3中time模块的用法及说明

python中，导入time模块使用的命令是

import time

你可以使用以下命令查看时间模块内置的可用方法：

dir(time)

可以使用以下命令查看时间模块中每个内置方法的说明：

help(time.time_method)

比如time模块下有一个time.time方法。现在想查看这个方法的官方文档，可以使用这个命令：

help(time.time)

时间的表示形式：

在python中，通常有三种表示时间的方式：时间戳、元组（结构化时间，struct_time）、格式化时间字符串。

(1)时间戳(timestamp)：一般来说，时间戳表示从1970年1月1日00:00:00开始计算的以秒为单位的偏移量，其值为float类型

（2）格式化的时间字符串(Format String):‘2017-06-20’

(3) 结构化时间（struct_time）：struct_time元组有九个元素：（年、月、日、时、分、秒、年中的星期、年中的天等）

time模块中内置的常用的方法：

asctime

接受一个时间元组并返回一个 24 个字符的可读形式的字符串“2017 年 5 月 30 日星期二 17:17:30”

Convert a time tuple to a string, e.g. 'Sat Jun 06 16:26:11 1998'.
When the time tuple is not present, current time as returned by localtime()
is used.
>>> time.asctime()
'Thu Jun 22 19:27:19 2017'

ctime

作用相当于asctime(localtime(secs)),未给参数相当于asctime()

ctime(seconds) -> string
Convert a time in seconds since the Epoch to a string in local time.
This is equivalent to asctime(localtime(seconds)). When the time tuple is
not present, current time as returned by localtime() is used.
>>> time.ctime()
'Thu Jun 22 19:34:35 2017'

gmtime

超时（自 1970 年以来经过的浮点秒数）并返回 GMT 时间元组 t（t.tm_isdst 始终为 0）

gmtime([seconds]) -> (tm_year, tm_mon, tm_mday, tm_hour, tm_min,
                       tm_sec, tm_wday, tm_yday, tm_isdst)
Convert seconds since the Epoch to a time tuple expressing UTC (a.k.a.
GMT).  When 'seconds' is not passed in, convert the current time instead.
If the platform supports the tm_gmtoff and tm_zone, they are available as
attributes only.
>>> time.gmtime()
time.struct_time(tm_year=2017, tm_mon=6, tm_mday=22, tm_hour=11, tm_min=35, tm_sec=12, tm_wday=3, 
tm_yday=173, tm_isdst=0)

localtime

接收时间（纪元 1970 后经过的浮点秒数）和本地时间返回时间元组 t（t.tm_isdst 可以是 0 或 1，取决于本地时间是否为夏令时）

localtime([seconds]) -> (tm_year,tm_mon,tm_mday,tm_hour,tm_min,
                          tm_sec,tm_wday,tm_yday,tm_isdst)
Convert seconds since the Epoch to a time tuple expressing local time.
When 'seconds' is not passed in, convert the current time instead.
>>> time.localtime()
time.struct_time(tm_year=2017, tm_mon=6, tm_mday=22, tm_hour=19, tm_min=35, tm_sec=35, 
tm_wday=3, tm_yday=173, tm_isdst=0)

mktime

接受时间元组并返回时间（自 1970 年以来经过的浮点秒数）

mktime(tuple) -> floating point number
Convert a time tuple in local time to seconds since the Epoch.
Note that mktime(gmtime(0)) will not generally return zero for most
time zones; instead the returned value will either be equal to that
of the timezone or altzone attributes on the time module.
>>> time.mktime(time.localtime())
1498131370.0

sleep

推迟调用线程的运行，secs的单位是秒

Delay execution for a given number of seconds.  The argument may be
a floating point number for subsecond precision.

strftime

将表示时间（由 time.localtime() 和 time.gmtime() 返回）的元组或 struct_time 转换为格式化的时间字符串。如果不指定t，则传入time.localtime()，如果元组中有元素越界，则抛出ValueError异常

strftime(format[, tuple]) -> string
Convert a time tuple to a string according to a format specification.
See the library reference manual for formatting codes. When the time tuple
is not present, current time as returned by localtime() is used.
    Commonly used format codes:
    
    %Y  Year with century as a decimal number.===>完整的年份
    %m  Month as a decimal number [01,12].===>月份(01-12)
    %d  Day of the month as a decimal number [01,31].===>一个月中的第几天(01-31)
    %H  Hour (24-hour clock) as a decimal number [00,23].===>一天中的第几个小时(24小时制，00-23)
    %M  Minute as a decimal number [00,59].===>分钟数(00-59)
    %S  Second as a decimal number [00,61].===>秒(01-61)
    %z  Time zone offset from UTC.===>用+HHMM或者-HHMM表示距离格林威治的时区偏移(H代表十进制的小时数，M代表十进制的分钟数)
    %a  Locale's abbreviated weekday name.===>本地(local)简化星期名称
    %A  Locale's full weekday name.===>本地完整星期名称
    %b  Locale's abbreviated month name.===>本地简化月份名称
    %B  Locale's full month name.===>本地完整月份名称
    %c  Locale's appropriate date and time representation.===>本地相应的日期和时间表示
    %I  Hour (12-hour clock) as a decimal number [01,12].===>一天中的第几个小时(12小时制，01-12)
    %p  Locale's equivalent of either AM or PM.===>本地am或者pm的相应符

>>> time.strftime("%Y-%m-%d")
'2017-06-22'
>>> time.strftime("%Y-%m-%d %H-%H-%S")
'2017-06-22 19-19-28'

strptim

将一个格式化的时间字符串转换为struct_time，其实就是strftie()的逆运算

strptime(string, format) -> struct_time
Parse a string to a time tuple according to a format specification.
See the library reference manual for formatting codes (same as
strftime()).
>>> time.strptime("2017-06-21","%Y-%m-%d")
time.struct_time(tm_year=2017, tm_mon=6, tm_mday=21, tm_hour=0, tm_min=0, tm_sec=0, tm_wday=2, tm_yday=172, tm_isdst=-1)
>>> time.strptime("2017-06-21 12-34-45","%Y-%m-%d %H-%M-%S")
time.struct_time(tm_year=2017, tm_mon=6, tm_mday=21, tm_hour=12, tm_min=34, tm_sec=45, tm_wday=2, tm_yday=172, tm_isdst=-1)
struct_time

把一个时间转换成结构化时间

The time value as returned by gmtime(), localtime(), and strptime(), and
accepted by asctime(), mktime() and strftime().  May be considered as a
sequence of 9 integers.
>>> time.struct_time(time.localtime())
time.struct_time(tm_year=2017, tm_mon=6, tm_mday=22, tm_hour=19, tm_min=42, tm_sec=7, 
tm_wday=3, tm_yday=173, tm_isdst=0)
time

返回当前时间的时间戳(1970元年后的浮点秒数

Return the current time in seconds since the Epoch.
Fractions of a second may be present if the system clock provides them.
>>> time.time()
1498131760.7711384
>>> time.time()
1498131764.7621822

几种时间形式的转换

１.把时间戳转换成结构化时间，使用的是time.localtime或time.gmtime命令。

>>> t1=time.time()
>>> print(t1)
1498132526.8227696
>>> t2=time.localtime(t1)
>>> print(t2)
time.struct_time(tm_year=2017, tm_mon=6, tm_mday=22, tm_hour=19, tm_min=55, tm_sec=26, 
tm_wday=3, tm_yday=173, tm_isdst=0)

２.把结构化时间转换成时间戳，使用time.mktime命令

>>> t3=time.struct_time(time.localtime())
>>> print(t3)
time.struct_time(tm_year=2017, tm_mon=6, tm_mday=22, tm_hour=19, tm_min=58, tm_sec=29, tm_wday=3, tm_yday=173, tm_isdst=0)
>>> t4=time.mktime(t3)
>>> print(t4)
1498132709.0

３.把结构化时间转换成时间字符串，使用time.strftime命令

>>> t1=time.localtime()
>>> print(t1)
time.struct_time(tm_year=2017, tm_mon=6, tm_mday=22, tm_hour=20, tm_min=0, tm_sec=37, tm_wday=3, 
tm_yday=173, tm_isdst=0)
>>> t2=time.strftime("%Y-%m-%d",t1)
>>> print(t2)
2017-06-22

4.将字符串时间转换为结构化时间，使用time.strptime命令

>>> t1="2017-05-20 08:08:10"
>>> print(t1)
2017-05-20 08:08:10
>>> t2=time.strptime(t1,"%Y-%m-%d %H:%M:%S"）
>>> print(t2)
time.struct_time(tm_year=2017, tm_mon=5, tm_mday=20, tm_hour=8, tm_min=8, tm_sec=10,
tm_wday=5, tm_yday=140, tm_isdst=-1)

例子：

如果我有一个时间字符串，然后想得到这个时间之后3天的时间字符串，我可以使用下面的命令：

import time
time1 = "2017-05-20"
#把时间字符串转换为时间戳，然后加上３天时间的秒数
time2 = time.mktime(time.strptime(time1,"%Y-%m-%d"))+3 * 24 * 3600
#把转换后的时间戳再转换成时间字符串
time3 = time.strftime("%Y-%m-%d", time.localtime(time2))
print(time3)