time --- 時間存取與轉換

---

這個模組提供了各種與時間相關的函式。若要查看相關功能，請參閱 datetime 和 calendar 模組。

雖然這個模組隨時可用，但並非所有函式在所有平台上都可用。這個模組中定義的大多數函式都會呼叫 C 語言平台的函式庫中具有相同名稱的函式。由於這些函式的語義因平台而異，所以偶爾查閱平台文件可能會有所幫助。

以下是對一些術語和慣例的說明。

• epoch 是起始的時間點，即 time.gmtime(0) 的回傳值。在所有平台上，它是 1970 年 1 月 1 日，00:00:00（UTC）。

• 術語 seconds since the epoch（紀元秒數） 是指從 epoch（紀元）開始經過的總秒數，通常不包括 leap seconds。在所有符合 POSIX 標準的平台上，leap seconds （閏秒）都不計入這個總數。

• 這個模組中的函式可能無法處理 epoch 之前或遙遠未來的日期和時間。未來的臨界點由 C 函式庫決定；對於 32 位元系統來說通常是在 2038 年。

• 函式 strptime() 在給定 %y 格式程式碼時可以解析兩位數的年份。當剖析兩位數的年份時，它們會根據 POSIX 和 ISO C 標準進行轉換：69--99 的值對映到 1969--1999，0--68 的值對映到 2000--2068。

• UTC 是 Coordinated Universal Time --- 世界協調時間（原稱為格林威治標準時間，或 GMT）。縮寫 UTC 並不是寫錯，而是英文和法文之間折衷的結果。

• DST 是 Daylight Saving Time（日光節約時間），一年中的某些時段（通常）將會時區調整一小時。DST 的規則是根據當地法律決定的，且可能每年不同。C 函式庫有一個包含當地規則的表（通常會為了靈活性而從系統文件中讀取），在這方面是唯一的真正依據。

• 各種即時 (real-time) 函式的精確度可能低於其值或引數所表示的單位所建議的精確度。例如，在大多數 Unix 系統上，時鐘每秒只「跳」50 次或 100 次。

• On the other hand, the precision of time() and sleep() is better than their Unix equivalents: times are expressed as floating-point numbers, time() returns the most accurate time available (using Unix gettimeofday() where available), and sleep() will accept a time with a nonzero fraction (Unix select() is used to implement this, where available).

• 由 gmtime()、localtime() 和 strptime() 回傳，並由 asctime()、mktime() 和 strftime() 接受的時間值，是一個 9 個整數的序列。gmtime()、localtime() 和 strptime() 的回傳值也為各個欄位提供屬性名稱。

  關於這些物件的敘述請見 struct_time。

  在 3.3 版的變更: 當平台支援對應的 struct tm 成員時，struct_time 型別被擴展以提供 tm_gmtoff 和 tm_zone 屬性。

  在 3.6 版的變更: struct_time 的屬性 tm_gmtoff 和 tm_zone 現在在所有平台上都可用。

• 使用以下函式在時間表示之間進行轉換：

  轉換來源	轉換目標	使用
  紀元秒數	世界協調時間的 struct_time	gmtime()
  紀元秒數	本地時間的 struct_time	localtime()
  世界協調時間的 struct_time	紀元秒數	calendar.timegm()
  本地時間的 struct_time	紀元秒數	mktime()

函式

time.asctime([t])

將由 gmtime() 或 localtime() 回傳的元組或 struct_time 表示的時間轉換為以下格式的字串：'Sun Jun 20 23:21:05 1993'。日期欄位為兩個字元長，如果日期是個位數，則用空格填充，例如：'Wed Jun  9 04:26:40 1993'。

如果沒有提供 t，則使用由 localtime() 回傳的當前時間。asctime() 不使用區域資訊。

備註

與同名的 C 函式不同，asctime() 不會添加結尾的換行字元。

time.pthread_getcpuclockid(thread_id)

為指定的 thread_id 回傳執行緒專用 CPU-time 時鐘的 clk_id。

使用 threading.get_ident() 或 threading.Thread 物件的 ident 屬性來獲取適用於 thread_id 的值。

警告

傳遞無效或過期的 thread_id 可能會導致未定義的行為，例如分段錯誤 (segmentation fault)。

適用：Unix

若需更多資訊，請參閱 pthread_getcpuclockid(3) 的說明文件。

在 3.7 版被加入.

time.clock_getres(clk_id)

回傳指定時鐘 clk_id 的解析度（精確度）。有關 clk_id 可接受的值的串列，請參閱 Clock ID Constants。

適用：Unix。

在 3.3 版被加入.

time.clock_gettime(clk_id) → float

回傳指定時鐘 clk_id 的時間。有關 clk_id 可接受的值的串列，請參閱 Clock ID Constants。

使用 clock_gettime_ns() 以避免 float 型別造成的精確度損失。

適用：Unix。

在 3.3 版被加入.

time.clock_gettime_ns(clk_id) → int

類似於 clock_gettime()，但回傳以奈秒 (nanoseconds) 為單位的時間。

適用：Unix。

在 3.7 版被加入.

time.clock_settime(clk_id, time: float)

設定指定時鐘 clk_id 的時間。目前，CLOCK_REALTIME 是 clk_id 唯一可以接受的值。

使用 clock_settime_ns() 以避免 float 型別造成的精確度損失。

適用：Unix。

在 3.3 版被加入.

time.clock_settime_ns(clk_id, time: int)

類似於 clock_settime()，但設定以奈秒為單位的時間。

適用：Unix。

在 3.7 版被加入.

time.ctime([secs])

將自 epoch 起以秒表示的時間轉換為表示當地時間且符合以下格式的字串：'Sun Jun 20 23:21:05 1993'。日期欄位為兩個字元長，如果日期是個位數，則用空格填充，例如：'Wed Jun  9 04:26:40 1993'。

如果未提供 secs 或其為 None，則使用由 time() 回傳的當前時間。ctime(secs) 等同於 asctime(localtime(secs))。ctime() 不使用區域資訊。

time.get_clock_info(name)

獲取指定時鐘的資訊作為命名空間物件。支援的時鐘名稱及讀取他們的值的對應函式如下：

• 'monotonic'：time.monotonic()

• 'perf_counter'：time.perf_counter()

• 'process_time'：time.process_time()

• 'thread_time'：time.thread_time()

• 'time'：time.time()

其結果具有以下屬性：

• adjustable: 如果時鐘可以自動（例如，透過 NTP 常駐程式）或由系統管理員手動更改，則為 True，否則為 False

• implementation: 用於獲取時鐘的值的底層 C 函式名稱。有關可能的值，請參閱 Clock ID Constants。

• monotonic: 如果時鐘不能倒轉，則為 True，否則為 False

• resolution: 以秒 (float) 為單位的時鐘的解析度

在 3.3 版被加入.

time.gmtime([secs])

將自 epoch 起以秒表示的時間轉換為 UTC 中的 struct_time，其中 dst 旗標始終為零。如果未提供 secs 或其為 None，則使用由 time() 回傳的當前時間。忽略秒的分數部分。關於 struct_time 物件的描述，請參閱上文。此函式的反運算請參閱 calendar.timegm()。

time.localtime([secs])

類似於 gmtime()，但轉換為當地時間。如果未提供 secs 或其為 None，則使用由 time() 回傳的當前時間。當 DST 適用於給定時間時，dst 旗標會被設定為 1。

如果時間戳超出 C 平台的 localtime() 或 gmtime() 函式支援的範圍，localtime() 可能會引發 OverflowError；在 localtime() 或 gmtime() 失敗時，會引發 OSError。通常會把年份限制在 1970 年到 2038 年之間。

time.mktime(t)

This is the inverse function of localtime(). Its argument is the struct_time or full 9-tuple (since the dst flag is needed; use -1 as the dst flag if it is unknown) which expresses the time in local time, not UTC. It returns a floating-point number, for compatibility with time(). If the input value cannot be represented as a valid time, either OverflowError or ValueError will be raised (which depends on whether the invalid value is caught by Python or the underlying C libraries). The earliest date for which it can generate a time is platform-dependent.

time.monotonic() → float

Return the value (in fractional seconds) of a monotonic clock, i.e. a clock that cannot go backwards. The clock is not affected by system clock updates. The reference point of the returned value is undefined, so that only the difference between the results of two calls is valid.

Use monotonic_ns() to avoid the precision loss caused by the float type.

在 3.3 版被加入.

在 3.5 版的變更: The function is now always available and always system-wide.

在 3.10 版的變更: On macOS, the function is now system-wide.

time.monotonic_ns() → int

Similar to monotonic(), but return time as nanoseconds.

在 3.7 版被加入.

time.perf_counter() → float

Return the value (in fractional seconds) of a performance counter, i.e. a clock with the highest available resolution to measure a short duration. It does include time elapsed during sleep and is system-wide. The reference point of the returned value is undefined, so that only the difference between the results of two calls is valid.

Use perf_counter_ns() to avoid the precision loss caused by the float type.

在 3.3 版被加入.

在 3.10 版的變更: On Windows, the function is now system-wide.

time.perf_counter_ns() → int

Similar to perf_counter(), but return time as nanoseconds.

在 3.7 版被加入.

time.process_time() → float

Return the value (in fractional seconds) of the sum of the system and user CPU time of the current process. It does not include time elapsed during sleep. It is process-wide by definition. The reference point of the returned value is undefined, so that only the difference between the results of two calls is valid.

Use process_time_ns() to avoid the precision loss caused by the float type.

在 3.3 版被加入.

time.process_time_ns() → int

Similar to process_time() but return time as nanoseconds.

在 3.7 版被加入.

time.sleep(secs)

Suspend execution of the calling thread for the given number of seconds. The argument may be a floating-point number to indicate a more precise sleep time.

If the sleep is interrupted by a signal and no exception is raised by the signal handler, the sleep is restarted with a recomputed timeout.

The suspension time may be longer than requested by an arbitrary amount, because of the scheduling of other activity in the system.

On Windows, if secs is zero, the thread relinquishes the remainder of its time slice to any other thread that is ready to run. If there are no other threads ready to run, the function returns immediately, and the thread continues execution. On Windows 8.1 and newer the implementation uses a high-resolution timer which provides resolution of 100 nanoseconds. If secs is zero, Sleep(0) is used.

Unix implementation:

• Use clock_nanosleep() if available (resolution: 1 nanosecond);

• Or use nanosleep() if available (resolution: 1 nanosecond);

• Or use select() (resolution: 1 microsecond).

在 3.5 版的變更: The function now sleeps at least secs even if the sleep is interrupted by a signal, except if the signal handler raises an exception (see PEP 475 for the rationale).

在 3.11 版的變更: On Unix, the clock_nanosleep() and nanosleep() functions are now used if available. On Windows, a waitable timer is now used.

time.strftime(format[, t])

Convert a tuple or struct_time representing a time as returned by gmtime() or localtime() to a string as specified by the format argument. If t is not provided, the current time as returned by localtime() is used. format must be a string. ValueError is raised if any field in t is outside of the allowed range.

0 is a legal argument for any position in the time tuple; if it is normally illegal the value is forced to a correct one.

The following directives can be embedded in the format string. They are shown without the optional field width and precision specification, and are replaced by the indicated characters in the strftime() result:

Directive	Meaning	註解
%a	Locale's abbreviated weekday name.
%A	Locale's full weekday name.
%b	Locale's abbreviated month name.
%B	Locale's full month name.
%c	Locale's appropriate date and time representation.
%d	Day of the month as a decimal number [01,31].
%f	Microseconds as a decimal number [000000,999999].	(1)
%H	Hour (24-hour clock) as a decimal number [00,23].
%I	Hour (12-hour clock) as a decimal number [01,12].
%j	Day of the year as a decimal number [001,366].
%m	Month as a decimal number [01,12].
%M	Minute as a decimal number [00,59].
%p	Locale's equivalent of either AM or PM.	(2)
%S	Second as a decimal number [00,61].	(3)
%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.	(4)
%w	Weekday as a decimal number [0(Sunday),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.	(4)
%x	Locale's appropriate date representation.
%X	Locale's appropriate time representation.
%y	Year without century as a decimal number [00,99].
%Y	Year with century as a decimal number.
%z	Time zone offset indicating a positive or negative time difference from UTC/GMT of the form +HHMM or -HHMM, where H represents decimal hour digits and M represents decimal minute digits [-23:59, +23:59]. [1]
%Z	Time zone name (no characters if no time zone exists). Deprecated. [1]
%%	A literal '%' character.

註解：

1. The %f format directive only applies to strptime(), not to strftime(). However, see also datetime.datetime.strptime() and datetime.datetime.strftime() where the %f format directive applies to microseconds.

2. When used with the strptime() function, the %p directive only affects the output hour field if the %I directive is used to parse the hour.

3. The range really is 0 to 61; value 60 is valid in timestamps representing leap seconds and value 61 is supported for historical reasons.

4. When used with the strptime() function, %U and %W are only used in calculations when the day of the week and the year are specified.

Here is an example, a format for dates compatible with that specified in the RFC 2822 Internet email standard. [1]

>>> from time import gmtime, strftime
>>> strftime("%a, %d %b %Y %H:%M:%S +0000", gmtime())
'Thu, 28 Jun 2001 14:17:15 +0000'

Additional directives may be supported on certain platforms, but only the ones listed here have a meaning standardized by ANSI C. To see the full set of format codes supported on your platform, consult the strftime(3) documentation.

On some platforms, an optional field width and precision specification can immediately follow the initial '%' of a directive in the following order; this is also not portable. The field width is normally 2 except for %j where it is 3.

time.strptime(string[, format])

Parse a string representing a time according to a format. The return value is a struct_time as returned by gmtime() or localtime().

The format parameter uses the same directives as those used by strftime(); it defaults to "%a %b %d %H:%M:%S %Y" which matches the formatting returned by ctime(). If string cannot be parsed according to format, or if it has excess data after parsing, ValueError is raised. The default values used to fill in any missing data when more accurate values cannot be inferred are (1900, 1, 1, 0, 0, 0, 0, 1, -1). Both string and format must be strings.

For example:

>>> import time
>>> time.strptime("30 Nov 00", "%d %b %y")   
time.struct_time(tm_year=2000, tm_mon=11, tm_mday=30, tm_hour=0, tm_min=0,
                 tm_sec=0, tm_wday=3, tm_yday=335, tm_isdst=-1)

Support for the %Z directive is based on the values contained in tzname and whether daylight is true. Because of this, it is platform-specific except for recognizing UTC and GMT which are always known (and are considered to be non-daylight savings timezones).

Only the directives specified in the documentation are supported. Because strftime() is implemented per platform it can sometimes offer more directives than those listed. But strptime() is independent of any platform and thus does not necessarily support all directives available that are not documented as supported.

class time.struct_time

The type of the time value sequence returned by gmtime(), localtime(), and strptime(). It is an object with a named tuple interface: values can be accessed by index and by attribute name. The following values are present:

Index	屬性	Values
0	tm_year	（例如 1993）
1	tm_mon	range [1, 12]
2	tm_mday	range [1, 31]
3	tm_hour	range [0, 23]
4	tm_min	range [0, 59]
5	tm_sec	range [0, 61]; see Note (2) in strftime()
6	tm_wday	range [0, 6]; Monday is 0
7	tm_yday	range [1, 366]
8	tm_isdst	0, 1 or -1; see below
N/A	tm_zone	abbreviation of timezone name
N/A	tm_gmtoff	offset east of UTC in seconds

Note that unlike the C structure, the month value is a range of [1, 12], not [0, 11].

In calls to mktime(), tm_isdst may be set to 1 when daylight savings time is in effect, and 0 when it is not. A value of -1 indicates that this is not known, and will usually result in the correct state being filled in.

When a tuple with an incorrect length is passed to a function expecting a struct_time, or having elements of the wrong type, a TypeError is raised.

time.time() → float

Return the time in seconds since the epoch as a floating-point number. The handling of leap seconds is platform dependent. On Windows and most Unix systems, the leap seconds are not counted towards the time in seconds since the epoch. This is commonly referred to as Unix time.

Note that even though the time is always returned as a floating-point number, not all systems provide time with a better precision than 1 second. While this function normally returns non-decreasing values, it can return a lower value than a previous call if the system clock has been set back between the two calls.

The number returned by time() may be converted into a more common time format (i.e. year, month, day, hour, etc...) in UTC by passing it to gmtime() function or in local time by passing it to the localtime() function. In both cases a struct_time object is returned, from which the components of the calendar date may be accessed as attributes.

Use time_ns() to avoid the precision loss caused by the float type.

time.time_ns() → int

Similar to time() but returns time as an integer number of nanoseconds since the epoch.

在 3.7 版被加入.

time.thread_time() → float

Return the value (in fractional seconds) of the sum of the system and user CPU time of the current thread. It does not include time elapsed during sleep. It is thread-specific by definition. The reference point of the returned value is undefined, so that only the difference between the results of two calls in the same thread is valid.

Use thread_time_ns() to avoid the precision loss caused by the float type.

適用：Linux、Unix、Windows。

Unix systems supporting CLOCK_THREAD_CPUTIME_ID.

在 3.7 版被加入.

time.thread_time_ns() → int

Similar to thread_time() but return time as nanoseconds.

在 3.7 版被加入.

time.tzset()

Reset the time conversion rules used by the library routines. The environment variable TZ specifies how this is done. It will also set the variables tzname (from the TZ environment variable), timezone (non-DST seconds West of UTC), altzone (DST seconds west of UTC) and daylight (to 0 if this timezone does not have any daylight saving time rules, or to nonzero if there is a time, past, present or future when daylight saving time applies).

適用：Unix。

備註

Although in many cases, changing the TZ environment variable may affect the output of functions like localtime() without calling tzset(), this behavior should not be relied on.

The TZ environment variable should contain no whitespace.

The standard format of the TZ environment variable is (whitespace added for clarity):

std offset [dst [offset [,start[/time], end[/time]]]]

Where the components are:

std 和 dst

Three or more alphanumerics giving the timezone abbreviations. These will be propagated into time.tzname

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) of 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 a Sunday.

time has the same format as 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. For example, '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')

Clock ID Constants

These constants are used as parameters for clock_getres() and clock_gettime().

time.CLOCK_BOOTTIME

Identical to CLOCK_MONOTONIC, except it also includes any time that the system is suspended.

This allows applications to get a suspend-aware monotonic clock without having to deal with the complications of CLOCK_REALTIME, which may have discontinuities if the time is changed using settimeofday() or similar.

適用：Linux 2.6.39 以上。

在 3.7 版被加入.

time.CLOCK_HIGHRES

The Solaris OS has a CLOCK_HIGHRES timer that attempts to use an optimal hardware source, and may give close to nanosecond resolution. CLOCK_HIGHRES is the nonadjustable, high-resolution clock.

適用：Solaris。

在 3.3 版被加入.

time.CLOCK_MONOTONIC

Clock that cannot be set and represents monotonic time since some unspecified starting point.

適用：Unix。

在 3.3 版被加入.

time.CLOCK_MONOTONIC_RAW

Similar to CLOCK_MONOTONIC, but provides access to a raw hardware-based time that is not subject to NTP adjustments.

適用：Linux 2.6.28 以上、macOS 10.12 以上。

在 3.3 版被加入.

time.CLOCK_PROCESS_CPUTIME_ID

High-resolution per-process timer from the CPU.

適用：Unix。

在 3.3 版被加入.

time.CLOCK_PROF

High-resolution per-process timer from the CPU.

適用：FreeBSD、NetBSD 7 以上、OpenBSD。

在 3.7 版被加入.

time.CLOCK_TAI

International Atomic Time

The system must have a current leap second table in order for this to give the correct answer. PTP or NTP software can maintain a leap second table.

適用：Linux。

在 3.9 版被加入.

time.CLOCK_THREAD_CPUTIME_ID

Thread-specific CPU-time clock.

適用：Unix。

在 3.3 版被加入.

time.CLOCK_UPTIME

Time whose absolute value is the time the system has been running and not suspended, providing accurate uptime measurement, both absolute and interval.

適用：FreeBSD、OpenBSD 5.5 以上。

在 3.7 版被加入.

time.CLOCK_UPTIME_RAW

Clock that increments monotonically, tracking the time since an arbitrary point, unaffected by frequency or time adjustments and not incremented while the system is asleep.

適用：macOS 10.12 以上。

在 3.8 版被加入.

The following constant is the only parameter that can be sent to clock_settime().

time.CLOCK_REALTIME

System-wide real-time clock. Setting this clock requires appropriate privileges.

適用：Unix。

在 3.3 版被加入.

Timezone Constants

time.altzone

The offset of the local DST timezone, in seconds west of UTC, if one is defined. This is negative if the local DST timezone is east of UTC (as in Western Europe, including the UK). Only use this if daylight is nonzero. See note below.

time.daylight

Nonzero if a DST timezone is defined. See note below.

time.timezone

The offset of the local (non-DST) timezone, in seconds west of UTC (negative in most of Western Europe, positive in the US, zero in the UK). See note below.

time.tzname

A tuple of two strings: the first is the name of the local non-DST timezone, the second is the name of the local DST timezone. If no DST timezone is defined, the second string should not be used. See note below.

備註

For the above Timezone constants (altzone, daylight, timezone, and tzname), the value is determined by the timezone rules in effect at module load time or the last time tzset() is called and may be incorrect for times in the past. It is recommended to use the tm_gmtoff and tm_zone results from localtime() to obtain timezone information.

也參考

datetime 模組

More object-oriented interface to dates and times.

locale 模組

Internationalization services. The locale setting affects the interpretation of many format specifiers in strftime() and strptime().

calendar 模組

General calendar-related functions. timegm() is the inverse of gmtime() from this module.

註解

[1] (1,2,3)

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.