Datetime module reference manual in Python

Preface

Python provides multiple built-in modules for manipulating date and time, such as calendar, time, and datetime. The interface provided by the time module is basically consistent with the C standard library time.h. Compared with the time module, the interface of the datetime module is more intuitive and easier to call.

The module defines two constants:

datetime.MINYEAR

datetime.MAXYEAR

These two constants respectively represent what datetime can represent The minimum and maximum year. Among them, MINYEAR = 1, MAXYEAR = 9999.

The datetime module defines the following classes:

datetime.date: a class representing dates. Commonly used attributes include year, month, day;

datetime.time: a class representing time. Commonly used attributes include hour, minute, second, microsecond;

datetime.datetime: represents date and time.

datetime.timedelta: represents the time interval, that is, the length between two time points.

datetime.tzinfo: Related information related to time zones.

Note: The types of objects listed above are all immutable.

date class

The date class represents a date (composed of year, month, day), and its prototype is as follows:

class datetime.date(year, month , day)

Parameter description: The range of

year is [MINYEAR, MAXYEAR], that is, [1, 9999]; the range of

month is [1 , 12]. (The month starts from 1, not from 0); The maximum value of

day is determined according to the given year and month parameters. For example, February in a leap year has 29 days; the

date class defines some commonly used class methods and class attributes:

date.max, date.min: what the date object can represent Maximum and minimum dates;

date.resolution: The date object represents the smallest unit of date. Here is the sky.

date.today(): Returns a date object representing the current local date;

date.fromtimestamp(timestamp): Returns a date object based on the given time stamp;

datetime.fromordinal(ordinal): Convert Gregorian calendar time to date object; (Gregorian Calendar: a calendar representation method, similar to our country’s lunar calendar, which is commonly used in Western countries and will not be discussed in detail here.)

Usage example:

>>> datetime.date.max
datetime.date(9999, 12, 31)
>>> datetime.date.min
datetime.date(1, 1, 1)
>>> datetime.date.resolution
datetime.timedelta(1)
>>> datetime.date.today()
datetime.date(2016, 5, 12)
>>> datetime.date.fromtimestamp(time.time())
datetime.date(2016, 5, 12)

Instance methods and properties provided by date:

date.year, date. month, date.day: year, month, day;

date.replace(year, month, day): Generate a new date object, replacing the original object with the year, month, and day specified by the parameters properties. (The original object remains unchanged)

date.timetuple(): Returns the time.struct_time object corresponding to the date;

date.toordinal(): Returns the Gregorian Calendar date corresponding to the date;

date.weekday(): Returns weekday, if it is Monday, returns 0; if it is Tuesday, returns 1, and so on;

data.isoweekday(): Returns weekday, If it is Monday, return 1; if it is Tuesday, return 2, and so on;

date.isocalendar(): Return a tuple in the format of (year, month, day);

date.isoformat(): Returns a string in the format of 'YYYY-MM-DD';

date.strftime(fmt): Custom format string.

Usage example:

>>> today = datetime.date.today()
>>> today.year
2016
>>> today.month
5
>>> today.day
12
>>> tomorrow = today.replace(day=13)
>>> tomorrow
datetime.date(2016, 5, 13)
>>> tomorrow.timetuple()
time.struct_time(tm_year=2016, tm_mon=5, tm_mday=13, tm_hour=0, tm_min=0, tm_sec=0, tm_wday=4, tm_yday=134, tm_isdst=-1)
>>> tomorrow.toordinal()
736097
>>> tomorrow.weekday()
4
>>> tomorrow.isoweekday()
5
>>> tomorrow.isocalendar()
(2016, 19, 5)
>>> tomorrow.isoformat()
'2016-05-13'
>>> tomorrow.strftime("%y-%m-%d")
'16-05-13'

date overloads the simple operator:

date allows for dates Perform additions, subtractions and comparisons:

date2 = date1 + timedelta:

Date plus an interval, returning a new date object

date2 = date1 - timedelta :

Dates are separated by intervals and a new date object is returned

timedelta = date1 - date2:

Subtract two dates and return one Time interval object

date1 < date2:

Compare two dates.

Usage example:

>>> now = datetime.date.today()
>>> now
datetime.date(2016, 5, 12)
>>> now += datetime.date.resolution
>>> now
datetime.date(2016, 5, 13)
>>> now -= datetime.date.resolution
>>> now
datetime.date(2016, 5, 12)
>>> now < datetime.date.max
True

Time class

The time class represents time (consisting of hours, minutes, seconds and microseconds Composition), its prototype is as follows:

class datetime.time(hour=0, minute=0, second=0, microsecond=0, tzinfo=None)

Parameter description: The range of

hour is [0, 24), the range of

minute is [0, 60), the range of

second is [0, 60),

The range of microsecond is [0, 1000000),

tzinfo represents time zone information.

Class attributes defined by the time class:

time.min, time.max: the minimum and maximum time that the time class can represent. Among them, time.min = time(0, 0, 0, 0), time.max = time(23, 59, 59, 999999);

time.resolution: The smallest unit of time, here is 1 Microseconds;

Usage example:

>>> datetime.time.min
datetime.time(0, 0)
>>> datetime.time.max
datetime.time(23, 59, 59, 999999)
>>> datetime.time.resolution
datetime.timedelta(0, 0, 1)

Instance methods and properties provided by the time class:

time .hour, time.minute, time.second, time.microsecond: hours, minutes, seconds, microseconds;

time.tzinfo: time zone information;

time.replace([hour[ , minute[, second[, microsecond[, tzinfo]]]]]): Create a new time object and replace the attributes in the original object with the hours, minutes, seconds, and microseconds specified by the parameters (the original object remains unchanged);

time.isoformat(): Returns a string representation in the format of "HH:MM:SS";

time.strftime(fmt): Returns a custom format String.

Usage example:

>>> tm = datetime.time(18, 18, 18)
>>> tm.hour
18
>>> tm.minute
18
>>> tm.second
18
>>> tm.microsecond
0
>>> tm.tzinfo
>>> tm.isoformat()
'18:18:18'
>>> tm.replace(hour=20)
datetime.time(20, 18, 18)
>>> tm.strftime("%I:%M:%S %p")
'06:18:18 PM'

Objects of the time class can only be compared and cannot be added or subtracted.

Datetime class

Datetime is a combination of date and time, including all information of date and time. Its prototype is as follows:

class datetime.datetime(year, month, day, hour=0, minute=0, second=0, microsecond=0, tzinfo=None)

各参数的含义与date、time的构造函数中的一样，要注意参数值的范围。

datetime类定义的类属性与方法：

datetime.min、datetime.max：datetime所能表示的最小值与最大值；

datetime.resolution：datetime最小单位；

datetime.today()：返回一个表示当前本地时间的datetime对象；

datetime.now([tz])：返回一个表示当前本地时间的datetime对象，如果提供了参数tz，则获取tz参数所指时区的本地时间；

datetime.utcnow()：返回一个当前utc时间的datetime对象；

datetime.fromtimestamp(timestamp[, tz])：根据时间戮创建一个datetime对象，参数tz指定时区信息；

datetime.utcfromtimestamp(timestamp)：根据时间戮创建一个datetime对象；

datetime.combine(date, time)：根据date和time，创建一个datetime对象；

datetime.strptime(date_string, format)：将格式字符串转换为datetime对象，data 与 time 类没有提供该方法。

使用示例：

>>> datetime.datetime.min
datetime.datetime(1, 1, 1, 0, 0)
>>> datetime.datetime.max
datetime.datetime(9999, 12, 31, 23, 59, 59, 999999)
>>> datetime.datetime.resolution
datetime.timedelta(0, 0, 1)
>>> print datetime.datetime.resolution
0:00:00.000001
>>> today = datetime.datetime.today()
>>> today
datetime.datetime(2016, 5, 12, 12, 46, 47, 246240)
>>> datetime.datetime.now()
datetime.datetime(2016, 5, 12, 12, 47, 9, 850643)
>>> datetime.datetime.utcnow()
datetime.datetime(2016, 5, 12, 4, 47, 42, 188124)
>>> datetime.datetime.fromtimestamp(time.time())
datetime.datetime(2016, 5, 12, 12, 48, 40, 459676)
>>> datetime.datetime.combine(datetime.date(1990, 10, 05), datetime.time(18, 18, 18))
datetime.datetime(1990, 10, 5, 18, 18, 18)
>>> datetime.datetime.strptime("2010-04-07 01:48:16.234000", "%Y-%m-%d %H:%M:%S .%f")
datetime.datetime(2010, 4, 7, 1, 48, 16, 234000)

datetime 的实例方法与属性

datetime类提供的实例方法与属性大部分功能与 date 和 time 类似，这里仅罗列方法名不再赘述：

datetime.year、month、day、hour、minute、second、microsecond、tzinfo：

datetime.date()：获取date对象；

datetime.time()：获取time对象；

datetime.replace([year[, month[, day[, hour[, minute[, second[, microsecond[, tzinfo]]]]]]]])：

**datetime.timetuple() **

**datetime.utctimetuple() **

datetime.toordinal()

datetime.weekday()

datetime.isocalendar()

datetime.isoformat([sep])

datetime.ctime()：返回一个日期时间的C格式字符串，等效于time.ctime(time.mktime(dt.timetuple()))；

datetime.strftime(format)

datetime 对象同样可以进行比较，或者相减返回一个时间间隔对象，或者日期时间加上一个间隔返回一个新的日期时间对象。

timedelta 类

datetime.timedelta 对象代表两个时间之间的的时间差，两个 date 或 datetime 对象相减时可以返回一个timedelta 对象。其原型如下：

class datetime.timedelta(days=0, seconds=0, microseconds=0, milliseconds=0, minutes=0, hours=0, weeks=0)

所有参数可选，且默认都是0，参数的值可以是整数，浮点数，正数或负数。

内部只存储days，seconds，microseconds，其他参数的值会自动按如下规则抓转换：

1 millisecond（毫秒） 转换成 1000 microseconds（微秒）

1 minute 转换成 60 seconds

1 hour 转换成 3600 seconds

1 week转换成 7 days

三个参数的取值范围分别为：

0 <= microseconds < 1000000

0 <= seconds < 3600*24 (the number of seconds in one day)

-999999999 <= days <= 999999999

timedelta 类定义的类属性：

timedelta.min：时间间隔对象的最小值,即 timedelta(-999999999).

timedelta.max：时间间隔对象的最大值，即 timedelta(days=999999999, hours=23, minutes=59, seconds=59, microseconds=999999).

timedelta.resolution：时间间隔的最小单位,即 timedelta(microseconds=1).

使用示例：

>>> datetime.timedelta.min
datetime.timedelta(-999999999)
>>> datetime.timedelta.max
datetime.timedelta(999999999, 86399, 999999)
>>> datetime.timedelta.resolution
datetime.timedelta(0, 0, 1)
>>> print datetime.timedelta.resolution
0:00:00.000001

timedelta 实例方法

timedelta.total_seconds()：计算时间间隔的总秒数

使用示例：

>>> datetime.timedelta.resolution.total_seconds()
1e-06

格式字符串

datetime、date、time 都提供了 strftime() 方法，该方法接收一个格式字符串，输出日期时间的字符串表示。支持的转换格式如下：

%a星期的简写。如 星期三为Web
%A星期的全写。如 星期三为Wednesday
%b月份的简写。如4月份为Apr
%B月份的全写。如4月份为April
%c: 日期时间的字符串表示。（如： 04/07/10 10:43:39）
%d: 日在这个月中的天数（是这个月的第几天）
%f: 微秒（范围[0,999999]）
%H: 小时（24小时制，[0, 23]）
%I: 小时（12小时制，[0, 11]）
%j: 日在年中的天数 [001,366]（是当年的第几天）
%m: 月份（[01,12]）
%M: 分钟（[00,59]）
%p: AM或者PM
%S: 秒（范围为[00,61]，为什么不是[00, 59]，参考python手册~_~）
%U: 周在当年的周数当年的第几周），星期天作为周的第一天
%w: 今天在这周的天数，范围为[0, 6]，6表示星期天
%W: 周在当年的周数（是当年的第几周），星期一作为周的第一天
%x: 日期字符串（如：04/07/10）
%X: 时间字符串（如：10:43:39）
%y: 2个数字表示的年份
%Y: 4个数字表示的年份
%z: 与utc时间的间隔 （如果是本地时间，返回空字符串）
%Z: 时区名称（如果是本地时间，返回空字符串）
%%: %% => %

使用示例：

>>> dt = datetime.datetime.now()
>>> dt.strftime('%Y-%m-%d %H:%M:%S %f')
'2016-05-12 14:19:22 333943'
>>> dt.strftime('%y-%m-%d %I:%M:%S %p')
'16-05-12 02:19:22 PM'
>>> dt.strftime("%a")
'Thu'
>>> dt.strftime("%A")
'Thursday'
>>> dt.strftime("%b")
'May'
>>> dt.strftime("%B")
'May'
>>> dt.strftime("%c")
'Thu May 12 14:19:22 2016'
>>> dt.strftime("%x")
'05/12/16'
>>> dt.strftime("%X")
'14:19:22'
>>> dt.strftime("%w")
'4'
>>> dt.strftime("%j")
'133'
>>> dt.strftime("%u")
'4'
>>> dt.strftime("%U")
'19'

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