笔记-python-standard library-8.1 data types-datetime

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笔记-python-standard library-8.1 data types-datetime

1.      Datatimes

本章节内容为日期和时间处理类和方法。

1.1.    datetime-basic date and time types

source code: Lib/datetime.py

datetime模块提供了日期和时间处理类，重点是各种格式化的输出。

时间包括两种，世界时和当地时间。

datetime和time对象可以选定时区。

datetime模块提供了下列常量：

datetime.MINYEAR，datetime.MAXYEAR分别是1和9999。

相关模块calendar日历功能，time时间访问和转换

1.1.1.   可用的类型

datetime.date:表示日期

datetime.time：表示时间

datetime.datetime：表示日期+时间

datetime.timedelta:表示两个日期，时间或日期+时间之间的差值

datetime.tzinfo：时区相关信息

datetime.timezone

类继承关系图：

object

    timedelta

    tzinfo

        timezone

    time

    date

        datetime

1.1.2.   timedelta objects

timedelta：两个时间之差。

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

实例属性（只读）：

支持的操作

实例方法：

timedelta.total_seconds() 返回时间差，以秒为单位。

1.1.3.   date objects

class datetime.date(year,month,day)

class methods:

date.today() 返回当日日期

date.fromtimestamp(timestamp) 根据时间戳返回日期

date.fromordinal(ordinal)              将Gregorian日历时间转换为date对象

class attributes:

date.year, date.month, date.day

supported operations:

instance methods:

date.replace(year=self.year, month=self.month, day=self.day)

根据参数返回一个替代后的日期。

date.timetuple()

Return a time.struct_time such as returned by time.localtime(). The hours, minutes and seconds are 0, and the DST flag is -1. d.timetuple()is equivalent to time.struct_time((d.year, d.month, d.day, 0, 0, 0, d.weekday(), yday, -1)), where yday = d.toordinal() - date(d.year, 1,1).toordinal() + 1 is the day number within the current year starting with 1 for January 1st.

示例：

>>> a = datetime.date(2017,3,22)

 >>> a.timetuple() time.struct_time(tm_year=2017, tm_mon=3, tm_mday=22, tm_hour=0, tm_min=0, tm_sec=0, tm_wday=2, tm_yday=81, tm_isdst=-1)

 >>> a.timetuple().tm_year

2017

>>> a.timetuple().tm_mon

3

>>> a.timetuple().tm_mday

22

date.weekday()

以数值形式返回星期，注意星期一是0，星期天是6。

date.isoweekday()

与上一函数相同，但星期数值是1-7

date.isocalendar()

Return a 3-tuple, (ISO year, ISO week number, ISO weekday).

date.isoformat()

Return a string representing the date in ISO 8601 format, ‘YYYY-MM-DD’. For example, date(2002, 12, 4).isoformat() == '2002-12-04'.

date.__str__()

等效于date.isoformat()

date.ctime()

返回特定格式的日期 date(2002, 12, 4).ctime() == 'Wed Dec 4 00:00:00 2002'.

date.strftime(format)

date.__format__(format)

都是返回特定格式的日期字符串。

下面是一些日期格式转换的示例：

>>> from datetime import date

>>> d = date.fromordinal(730920) # 730920th day after 1. 1. 0001

>>> d

datetime.date(2002, 3, 11)

>>> t = d.timetuple()

>>> for i in t:    

...     print(i)

2002                # year

3                   # month

11                  # day

0

0

0

0                   # weekday (0 = Monday)

70                  # 70th day in the year

-1

>>> ic = d.isocalendar()

>>> for i in ic:   

...     print(i)

2002                # ISO year

11                  # ISO week number

1                   # ISO day number ( 1 = Monday )

>>> d.isoformat()

'2002-03-11'

>>> d.strftime("%d/%m/%y")

'11/03/02'

>>> d.strftime("%A %d. %B %Y")

'Monday 11. March 2002'

>>> 'The {1} is {0:%d}, the {2} is {0:%B}.'.format(d, "day", "month")

'The day is 11, the month is March.'

1.1.4.   datetime objects

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

class methods:

datetime.today()

返回日期时间，结果如下：datetime.datetime(2018, 9, 29, 21, 16, 9, 954626)

datetime.now(tz=None)

返回日期时间，如果tz非空，返回一个tzinfo子类，时间进行转换。

datetime.utcnow() 返回utc时间。

datetime.fromtimestamp(timestamp, ta=None) 根据给出的时间戳返回时日期时间。

datetime.utcfromtimestamp(timestamp) 返回utc日期时间

datetime.fromordinal(ordinal)       返回Gregorian日期时间

datetime.combine(date,time.tzinfo=self.tzinfo) 将date和time对象合并成datetime对象

datetime.strptime(date_string, format)      根据参数，返回datetime对象

class attributes:

datetime.year    

datetime.month

datetime.day

datetime.hour

datetime.minute

datetime.second

datetime.microsecond

datetime.tzinfo

datetime.fold

support operations:

instance methods:

date(),time(),timetz(),

replace(year=self.year, month=self.month, day=self.day, hour=self.hour, minute=self.minute, second=self.second, microsecond=self.microsecond, tzinfo=self.tzinfo, * fold=0)

astimezone(tz=None)

utcoffset(), dst(),tzname(), timetuple(),utctimetuple()

timestamp()

weekday()

isoweekday()

isocalendar()

isoformat(sep=’T’, timespec=’auto’)

__str__()

ctime()

strftime(format)

__format__(format)

Examples of working with datetime objects:

>>> 

>>> from datetime import datetime, date, time

>>> # Using datetime.combine()

>>> d = date(2005, 7, 14)

>>> t = time(12, 30)

>>> datetime.combine(d, t)

datetime.datetime(2005, 7, 14, 12, 30)

>>> # Using datetime.now() or datetime.utcnow()

>>> datetime.now()  

datetime.datetime(2007, 12, 6, 16, 29, 43, 79043)   # GMT +1

>>> datetime.utcnow()  

datetime.datetime(2007, 12, 6, 15, 29, 43, 79060)

>>> # Using datetime.strptime()

>>> dt = datetime.strptime("21/11/06 16:30", "%d/%m/%y %H:%M")

>>> dt

datetime.datetime(2006, 11, 21, 16, 30)

>>> # Using datetime.timetuple() to get tuple of all attributes

>>> tt = dt.timetuple()

>>> for it in tt:  

...     print(it)

...

2006    # year

11      # month

21      # day

16      # hour

30      # minute

0       # second

1       # weekday (0 = Monday)

325     # number of days since 1st January

-1      # dst - method tzinfo.dst() returned None

>>> # Date in ISO format

>>> ic = dt.isocalendar()

>>> for it in ic:  

...     print(it)

...

2006    # ISO year

47      # ISO week

2       # ISO weekday

>>> # Formatting datetime

>>> dt.strftime("%A, %d. %B %Y %I:%M%p")

'Tuesday, 21. November 2006 04:30PM'

>>> 'The {1} is {0:%d}, the {2} is {0:%B}, the {3} is {0:%I:%M%p}.'.format(dt, "day", "month", "time")

'The day is 21, the month is November, the time is 04:30PM.'

Using datetime with tzinfo:

>>> 

>>> from datetime import timedelta, datetime, tzinfo

>>> class GMT1(tzinfo):

...     def utcoffset(self, dt):

...         return timedelta(hours=1) + self.dst(dt)

...     def dst(self, dt):

...         # DST starts last Sunday in March

...         d = datetime(dt.year, 4, 1)   # ends last Sunday in October

...         self.dston = d - timedelta(days=d.weekday() + 1)

...         d = datetime(dt.year, 11, 1)

...         self.dstoff = d - timedelta(days=d.weekday() + 1)

...         if self.dston <=  dt.replace(tzinfo=None) < self.dstoff:

...             return timedelta(hours=1)

...         else:

...             return timedelta(0)

...     def tzname(self,dt):

...          return "GMT +1"

...

>>> class GMT2(tzinfo):

...     def utcoffset(self, dt):

...         return timedelta(hours=2) + self.dst(dt)

...     def dst(self, dt):

...         d = datetime(dt.year, 4, 1)

...         self.dston = d - timedelta(days=d.weekday() + 1)

...         d = datetime(dt.year, 11, 1)

...         self.dstoff = d - timedelta(days=d.weekday() + 1)

...         if self.dston <=  dt.replace(tzinfo=None) < self.dstoff:

...             return timedelta(hours=1)

...         else:

...             return timedelta(0)

...     def tzname(self,dt):

...         return "GMT +2"

...

>>> gmt1 = GMT1()

>>> # Daylight Saving Time

>>> dt1 = datetime(2006, 11, 21, 16, 30, tzinfo=gmt1)

>>> dt1.dst()

datetime.timedelta(0)

>>> dt1.utcoffset()

datetime.timedelta(0, 3600)

>>> dt2 = datetime(2006, 6, 14, 13, 0, tzinfo=gmt1)

>>> dt2.dst()

datetime.timedelta(0, 3600)

>>> dt2.utcoffset()

datetime.timedelta(0, 7200)

>>> # Convert datetime to another time zone

>>> dt3 = dt2.astimezone(GMT2())

>>> dt3    

datetime.datetime(2006, 6, 14, 14, 0, tzinfo=<GMT2 object at 0x...>)

>>> dt2    

datetime.datetime(2006, 6, 14, 13, 0, tzinfo=<GMT1 object at 0x...>)

>>> dt2.utctimetuple() == dt3.utctimetuple()

True

1.1.5.   time objects

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

instance attributes(read-only):

hour,minute,second,microsecond,tzinfo,fold

supported operations:

1. comparison of time to time.
2. hash, use as dict key
3. efficent pickling

instance methods:与date,datetime没什么太大不同，不重复了。

1.1.6.   strftime() and strptime() behavior

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