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。
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 in UTC | gmtime() |
| 从纪元起的秒数 | struct_time in local time | localtime() |
| struct_time in UTC | 从纪元起的秒数 | calendar.timegm() |
| struct_time in local time | 从纪元起的秒数 | mktime() |
The module defines the following functions and data items:
Boolean value indicating whether two-digit year values will be accepted. This is true by default, but will be set to false if the environment variable PYTHONY2K has been set to a non-empty string. It may also be modified at run time.
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.
转换元组或 struct_time 表示时间如返回通过 gmtime() or localtime() to a 24-character string of the following form: 'Sun Jun 20 23:21:05 1993' 。若 t 不提供，当前时间如返回通过 localtime() is used. Locale information is not used by asctime() .
注意
Unlike the C function of the same name, there is no trailing newline.
Changed in version 2.1: Allowed t to be omitted.
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.
Convert a time expressed in seconds since the epoch to a string representing local time. If secs 不提供或 None ，当前时间若返回通过 time() 被使用。 ctime(secs) 相当于 asctime(localtime(secs)) 。不使用区域设置信息通过 ctime() .
Changed in version 2.1: Allowed secs to be omitted.
2.4 版改变： 若 secs is None , the current time is used.
Nonzero if a DST timezone is defined.
Convert a time expressed in seconds since the epoch to a struct_time in UTC in which the dst flag is always zero. If secs 不提供或 None ，当前时间若返回通过 time() is used. Fractions of a second are ignored. See above for a description of the struct_time 对象。见 calendar.timegm() for the inverse of this function.
Changed in version 2.1: Allowed secs to be omitted.
2.4 版改变： 若 secs is None , the current time is used.
像 gmtime() 但转换为本地时间。若 secs 不提供或 None ，当前时间若返回通过 time() 的使用。dst 标志被设为 1 当 DST (夏令时) 适用于给定时间时。
Changed in version 2.1: Allowed secs to be omitted.
2.4 版改变： 若 secs is None , the current time is used.
这是逆函数对于 localtime() 。它的自变量为 struct_time 或完整 9 元组 (由于需要 dst 标志；使用 -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.
Suspend execution for the given number of seconds. The argument may be a floating point number to indicate a more precise sleep time. The actual suspension time may be less than that requested because any caught signal will terminate the sleep() 之后执行相应信号的捕获例程。此外，挂起时间可能长于任意请求数量，由于其它系统活动的调度。
转换元组或 struct_time 表示时间如返回通过 gmtime() or localtime() 到字符串作为指定通过 format 自变量。若 t 不提供，当前时间如返回通过 localtime() 被使用。 format 必须是字符串。 ValueError 被引发若任何字段在 t 超出允许范围。 strftime() returns a locale depedent byte string; the result may be converted to unicode by doing strftime(<myformat>).decode(locale.getlocale()[1]) .
Changed in version 2.1: Allowed t to be omitted.
2.4 版改变： ValueError raised if a field in t 超出范围。
Changed in version 2.5: 0 is now a legal argument for any position in the time tuple; if it is normally illegal the value is forced to a correct one.
下列指令可以嵌入 format 字符串。它们被展示时没有可选字段宽度和精度规范，并替换指示字符在 strftime() 结果：
| 指令 | 含义 | 注意事项 |
|---|---|---|
| %a | Locale’s abbreviated weekday 名称。 | |
| %A | 区域设置的完整工作日名称。 | |
| %b | Locale’s abbreviated month 名称。 | |
| %B | 区域设置的完整月份名。 | |
| %c | Locale’s appropriate date and time representation. | |
| %d | Day of the month as a decimal number [01,31]. | |
| %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. | (1) |
| %S | Second as a decimal number [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 | 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. | (3) |
| %x | Locale’s appropriate date 表示。 | |
| %X | Locale’s appropriate time 表示。 | |
| %y | Year without century as a decimal number [00,99]. | |
| %Y | Year with century as a decimal 编号。 | |
| %Z | Time zone name (no characters if no time zone exists). | |
| %% | 文字 '%' 字符。 |
注意事项：
Here is an example, a format for dates compatible with that specified in the RFC 2822 互联网 Email 标准。 [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) 文档编制。
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.
根据格式剖析表示时间的字符串。返回值为 struct_time 如返回通过 gmtime() or localtime() .
The format 参数使用相同指令如那些用于 strftime() ；默认为 "%a %b %d %H:%M:%S %Y" which matches the formatting returned by ctime() 。若 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) .
例如：
>>> 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)
支持 %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.
时间值序列类型返回通过 gmtime() , localtime() ，和 strptime() 。它是对象具有 命名元组 interface: values can be accessed by index and by attribute name. The following values are present:
| 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 |
2.2 版新增。
Note that unlike the C structure, the month value is a range of [1, 12], not [0, 11]. A year value will be handled as described under 2000 年 (Y2K) 问题 above. A -1 argument as the daylight savings flag, passed to mktime() will usually result in the correct daylight savings state to be 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 被引发。
Return the time in seconds since the epoch as a floating point number. 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 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).
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.
Resets the time conversion rules used by the library routines. The environment variable TZ specifies how this is done.
2.3 版新增。
可用性：Unix。
注意
Although in many cases, changing the TZ environment variable may affect the output of functions like localtime() 不调用 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:
Indicates when to change to and back from DST. The format of the start and end dates are one of the following:
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
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 . |
