15.3. `time` — 时间的访问和转换 ¶

此模块提供各种时间相关函数。对于相关功能，另请参阅 datetime and calendar 模块。

Although this module is always available, not all functions are available on all platforms. Most of the functions defined in this module call platform C library functions with the same name. It may sometimes be helpful to consult the platform documentation, because the semantics of these functions varies among platforms.

按次序解释一些术语和约定。

The epoch is the point where the time starts. On January 1st of that year, at 0 hours, the “time since the epoch” is zero. For Unix, the epoch is 1970. To find out what the epoch is, look at gmtime(0) .

The functions in this module do not handle dates and times before the epoch or far in the future. The cut-off point in the future is determined by the C library; for Unix, it is typically in 2038.

2000 年 (Y2K) 问题 : Python depends on the platform’s C library, which generally doesn’t have year 2000 issues, since all dates and times are represented internally as seconds since the epoch. Functions accepting a struct_time (see below) generally require a 4-digit year. For backward compatibility, 2-digit years are supported if the module variable accept2dyear is a non-zero integer; this variable is initialized to 1 unless the environment variable PYTHONY2K is set to a non-empty string, in which case it is initialized to 0 . Thus, you can set PYTHONY2K to a non-empty string in the environment to require 4-digit years for all year input. When 2-digit years are accepted, they are converted according to the POSIX or X/Open standard: values 69-99 are mapped to 1969-1999, and values 0–68 are mapped to 2000–2068. Values 100–1899 are always illegal.

UTC is Coordinated Universal Time (formerly known as Greenwich Mean Time, or GMT). The acronym UTC is not a mistake but a compromise between English and French.

DST is Daylight Saving Time, an adjustment of the timezone by (usually) one hour during part of the year. DST rules are magic (determined by local law) and can change from year to year. The C library has a table containing the local rules (often it is read from a system file for flexibility) and is the only source of True Wisdom in this respect.
The precision of the various real-time functions may be less than suggested by the units in which their value or argument is expressed. E.g. on most Unix systems, the clock “ticks” only 50 or 100 times a second.
另一方面，精度对于 time() and sleep() 比它们的 Unix 等价要好：时间以浮点数形式表达， time() 返回最精确可用时间 (使用 Unix gettimeofday() 若可用)，而 sleep() 将接受具有非零小数的时间 (Unix select() 用于实现这，若可用)。
时间值如返回通过 gmtime() , localtime() ，和 strptime() ，和接受通过 asctime() , mktime() and strftime() , may be considered as a sequence of 9 integers. The return values of gmtime() , localtime() ，和 strptime() 还为单个字段提供属性名。

见 struct_time 了解这些对象的描述。

2.2 版改变： The time value sequence was changed from a tuple to a struct_time , with the addition of attribute names for the fields.

使用下列函数在时间表示之间转换：

从	到	使用
从纪元起的秒数	`struct_time` 按 UTC	`gmtime()`
从纪元起的秒数	`struct_time` 按本地时间	`localtime()`
`struct_time` 按 UTC	从纪元起的秒数	`calendar.timegm()`
`struct_time` 按本地时间	从纪元起的秒数	`mktime()`

The module defines the following functions and data items:

time. accept2dyear ¶

time. altzone ¶

time. asctime ( [ t ] ) ¶

time. clock ( ) ¶

On Unix, return the current processor time as a floating point number expressed in seconds. The precision, and in fact the very definition of the meaning of “processor time”, depends on that of the C function of the same name, but in any case, this is the function to use for benchmarking Python or timing algorithms.

On Windows, this function returns wall-clock seconds elapsed since the first call to this function, as a floating point number, based on the Win32 function QueryPerformanceCounter() . The resolution is typically better than one microsecond.

time. ctime ( [ secs ] ) ¶

time. daylight ¶

time. gmtime ( [ secs ] ) ¶

time. localtime ( [ secs ] ) ¶

time. mktime ( t ) ¶

time. sleep ( secs ) ¶

time. strftime ( format [ , t ] ) ¶

指令	含义	注意事项
`%a`	区域设置的缩写工作日名称。
`%A`	区域设置的完整工作日名称。
`%b`	区域设置的缩写月份名。
`%B`	区域设置的完整月份名。
`%c`	区域设置的适当日期和时间表示。
`%d`	月份日期如十进制数 [01, 31]。
`%H`	小时 (24 小时时钟) 如十进制数 [00, 23]。
`%I`	小时 (12 小时时钟) 如十进制数 [01, 12]。
`%j`	年内天数如十进制数 [001, 366]。
`%m`	月份如十进制数 [01, 12]。
`%M`	分钟如十进制数 [00, 59]。
`%p`	区域设置的 AM 或 PM 等价。	(1)
`%S`	秒如十进制数 [00, 61]。	(2)
`%U`	Week number of the year (Sunday as the first day of the week) as a decimal number [00,53]. All days in a new year preceding the first Sunday are considered to be in week 0.	(3)
`%w`	工作日如十进制数 [0 (星期日）, 6]。
`%W`	Week number of the year (Monday as the first day of the week) as a decimal number [00,53]. All days in a new year preceding the first Monday are considered to be in week 0.	(3)
`%x`	区域设置的适当日期表示。
`%X`	区域设置的适当时间表示。
`%y`	不带世纪的年份如十进制数 [00, 99]。
`%Y`	带有世纪的年份如十进制数。
`%Z`	时区名称 (没有字符若不存在时区)。
`%%`	文字 `'%'` 字符。

time. strptime ( string [ , format ] ) ¶

class time. struct_time ¶

索引	属性	值
0	`tm_year`	(例如，1993)
1	`tm_mon`	范围 [1, 12]
2	`tm_mday`	范围 [1, 31]
3	`tm_hour`	范围 [0, 23]
4	`tm_min`	范围 [0, 59]
5	`tm_sec`	范围 [0, 61]；见 (2) in `strftime()` description
6	`tm_wday`	range [0, 6]，星期一为 0
7	`tm_yday`	范围 [1, 366]
8	`tm_isdst`	0, 1 or -1; see below

time. time ( ) ¶

time. timezone ¶

time. tzname ¶

time. tzset ( ) ¶

std and dst
offset: The offset has the form: ± hh[:mm[:ss]] . This indicates the value added the local time to arrive at UTC. If preceded by a ‘-‘, the timezone is east of the Prime Meridian; otherwise, it is west. If no offset follows dst, summer time is assumed to be one hour ahead of standard time.
start[/time], end[/time]: Indicates when to change to and back from DST. The format of the start and end dates are one of the following:

Jn: The Julian day n (1 <= n <= 365). Leap days are not counted, so in all years February 28 is day 59 and March 1 is day 60.
n: The zero-based Julian day (0 <= n <= 365). Leap days are counted, and it is possible to refer to February 29.
Mm.n.d: The d ’th day (0 <= d <= 6) or week n of month m of the year (1 <= n <= 5, 1 <= m <= 12, where week 5 means “the last d day in month m ” which may occur in either the fourth or the fifth week). Week 1 is the first week in which the d ’th day occurs. Day zero is Sunday.

time 拥有相同格式如 offset except that no leading sign (‘-‘ or ‘+’) is allowed. The default, if time is not given, is 02:00:00.

>>> os.environ['TZ'] = 'EST+05EDT,M4.1.0,M10.5.0'
>>> time.tzset()
>>> time.strftime('%X %x %Z')
'02:07:36 05/08/03 EDT'
>>> os.environ['TZ'] = 'AEST-10AEDT-11,M10.5.0,M3.5.0'
>>> time.tzset()
>>> time.strftime('%X %x %Z')
'16:08:12 05/08/03 AEST'

On many Unix systems (including *BSD, Linux, Solaris, and Darwin), it is more convenient to use the system’s zoneinfo ( tzfile(5) ) database to specify the timezone rules. To do this, set the TZ environment variable to the path of the required timezone datafile, relative to the root of the systems ‘zoneinfo’ timezone database, usually located at /usr/share/zoneinfo 。例如， 'US/Eastern' , 'Australia/Melbourne' , 'Egypt' or 'Europe/Amsterdam' .

>>> os.environ['TZ'] = 'US/Eastern'
>>> time.tzset()
>>> time.tzname
('EST', 'EDT')
>>> os.environ['TZ'] = 'Egypt'
>>> time.tzset()
>>> time.tzname
('EET', 'EEST')

另请参阅

模块 datetime
模块 locale: Internationalization services. The locale setting affects the interpretation of many format specifiers in strftime() and strptime() .
模块 calendar: 一般日历相关功能。 timegm() is the inverse of gmtime() 来自此模块。

脚注

1: The use of %Z is now deprecated, but the %z escape that expands to the preferred hour/minute offset is not supported by all ANSI C libraries. Also, a strict reading of the original 1982 RFC 822 standard calls for a two-digit year (%y rather than %Y), but practice moved to 4-digit years long before the year 2000. After that, RFC 822 became obsolete and the 4-digit year has been first recommended by RFC 1123 and then mandated by RFC 2822 .

15.3. time — 时间的访问和转换 ¶

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15.3. `time` — 时间的访问和转换 ¶