Introduction to the datetime module in Python (with examples)

This article brings you an introduction to the datetime module in Python (with examples). It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

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 the minimum and maximum year that datetime can represent. Among them, MINYEAR = 1, MAXYEAR = 9999.

datetime The module defines the following classes:

• datetime.date: Class representing date. 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: Indicates the time interval, that is, the length between two time points.

• datetime.tzinfo: Relevant information related to time zones.

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

date class

date class represents a date (composed of year, month, and 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 attributes:

• date. max, date.min: the maximum and minimum date that the date object can represent;

• date.resolution: date object The smallest unit representing a date. Here is the sky.

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

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

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

Usage examples: Instance methods and properties provided by

>>> 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)

date:

• ##date.year, date.month, date.day: Year, month, day;

• date.replace(year, month, day): Generate a new date object, use The year, month, and day specified by the parameters replace the attributes in the original object. (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, return 0; if it is Tuesday, return 1, and so on;

• data.isoweekday(): Return weekday, if On Monday, 1 is returned; if it is Tuesday, 2 is returned, and so on;

• date.isocalendar(): The return format is such as (year, month, day) tuple;

• 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 addition, subtraction and comparison of dates:

• date2 = date1 timedelta：

Add an interval to the date and return a new date object

• date2 = date1 - timedelta：

The date is separated by an interval and returns a new date object

• timedelta = date1 - date2：

Subtract two dates and return a 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

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

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

Parameter description:

• hour 的范围为[0, 24),

• minute 的范围为[0, 60)，

• second 的范围为[0, 60)，

• microsecond 的范围为[0, 1000000),

• tzinfo 表示时区信息。

time 类定义的类属性：

• time.min、time.max：time类所能表示的最小、最大时间。其中，time.min = time(0, 0, 0, 0)， time.max = time(23, 59, 59, 999999)；

• time.resolution：时间的最小单位，这里是1微秒；

使用示例：

>>> datetime.time.min
datetime.time(0, 0)
>>> datetime.time.max
datetime.time(23, 59, 59, 999999)
>>> datetime.time.resolution
datetime.timedelta(0, 0, 1)</p>
<h4 id="time类提供的实例方法和属性">time类提供的实例方法和属性：</h4>
<ul class=" list-paddingleft-2">
<li><p><strong>time.hour</strong>、<strong>time.minute</strong>、<strong>time.second</strong>、<strong>time.microsecond</strong>：时、分、秒、微秒；</p></li>
<li><p><strong>time.tzinfo</strong>：时区信息；</p></li>
<li><p><strong>time.replace</strong>([hour[, minute[, second[, microsecond[, tzinfo]]]]])：创建一个新的时间对象，用参数指定的时、分、秒、微秒代替原有对象中的属性（原有对象仍保持不变）；</p></li>
<li><p><strong>time.isoformat()</strong>：返回型如"HH:MM:SS"格式的字符串表示；</p></li>
<li><p><strong>time.strftime(fmt)</strong>：返回自定义格式化字符串。</p></li>
</ul>
<p>使用示例：</p>
<pre class="brush:php;toolbar:false">>>> 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'

time 类的对象只能进行比较，无法进行加减操作。

datetime 类

datetime 是 date 与 time 的结合体，包括 date 与 time 的所有信息。其原型如下：

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</p>
<h4 id="timedelta-实例方法">timedelta 实例方法</h4>
<ul class=" list-paddingleft-2"><li><p><strong>timedelta.total_seconds()</strong>：计算时间间隔的总秒数</p></li></ul>
<p>使用示例：</p>
<pre class="brush:php;toolbar:false">>>> 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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