/Doc/library/datetime.rst
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- :mod:`datetime` --- Basic date and time types
- =============================================
- .. module:: datetime
- :synopsis: Basic date and time types.
- .. moduleauthor:: Tim Peters <tim@zope.com>
- .. sectionauthor:: Tim Peters <tim@zope.com>
- .. sectionauthor:: A.M. Kuchling <amk@amk.ca>
- .. XXX what order should the types be discussed in?
- .. versionadded:: 2.3
- The :mod:`datetime` module supplies classes for manipulating dates and times in
- both simple and complex ways. While date and time arithmetic is supported, the
- focus of the implementation is on efficient member extraction for output
- formatting and manipulation. For related
- functionality, see also the :mod:`time` and :mod:`calendar` modules.
- There are two kinds of date and time objects: "naive" and "aware". This
- distinction refers to whether the object has any notion of time zone, daylight
- saving time, or other kind of algorithmic or political time adjustment. Whether
- a naive :class:`datetime` object represents Coordinated Universal Time (UTC),
- local time, or time in some other timezone is purely up to the program, just
- like it's up to the program whether a particular number represents metres,
- miles, or mass. Naive :class:`datetime` objects are easy to understand and to
- work with, at the cost of ignoring some aspects of reality.
- For applications requiring more, :class:`datetime` and :class:`time` objects
- have an optional time zone information member, :attr:`tzinfo`, that can contain
- an instance of a subclass of the abstract :class:`tzinfo` class. These
- :class:`tzinfo` objects capture information about the offset from UTC time, the
- time zone name, and whether Daylight Saving Time is in effect. Note that no
- concrete :class:`tzinfo` classes are supplied by the :mod:`datetime` module.
- Supporting timezones at whatever level of detail is required is up to the
- application. The rules for time adjustment across the world are more political
- than rational, and there is no standard suitable for every application.
- The :mod:`datetime` module exports the following constants:
- .. data:: MINYEAR
- The smallest year number allowed in a :class:`date` or :class:`datetime` object.
- :const:`MINYEAR` is ``1``.
- .. data:: MAXYEAR
- The largest year number allowed in a :class:`date` or :class:`datetime` object.
- :const:`MAXYEAR` is ``9999``.
- .. seealso::
- Module :mod:`calendar`
- General calendar related functions.
- Module :mod:`time`
- Time access and conversions.
- Available Types
- ---------------
- .. class:: date
- An idealized naive date, assuming the current Gregorian calendar always was, and
- always will be, in effect. Attributes: :attr:`year`, :attr:`month`, and
- :attr:`day`.
- .. class:: time
- An idealized time, independent of any particular day, assuming that every day
- has exactly 24\*60\*60 seconds (there is no notion of "leap seconds" here).
- Attributes: :attr:`hour`, :attr:`minute`, :attr:`second`, :attr:`microsecond`,
- and :attr:`tzinfo`.
- .. class:: datetime
- A combination of a date and a time. Attributes: :attr:`year`, :attr:`month`,
- :attr:`day`, :attr:`hour`, :attr:`minute`, :attr:`second`, :attr:`microsecond`,
- and :attr:`tzinfo`.
- .. class:: timedelta
- A duration expressing the difference between two :class:`date`, :class:`time`,
- or :class:`datetime` instances to microsecond resolution.
- .. class:: tzinfo
- An abstract base class for time zone information objects. These are used by the
- :class:`datetime` and :class:`time` classes to provide a customizable notion of
- time adjustment (for example, to account for time zone and/or daylight saving
- time).
- Objects of these types are immutable.
- Objects of the :class:`date` type are always naive.
- An object *d* of type :class:`time` or :class:`datetime` may be naive or aware.
- *d* is aware if ``d.tzinfo`` is not ``None`` and ``d.tzinfo.utcoffset(d)`` does
- not return ``None``. If ``d.tzinfo`` is ``None``, or if ``d.tzinfo`` is not
- ``None`` but ``d.tzinfo.utcoffset(d)`` returns ``None``, *d* is naive.
- The distinction between naive and aware doesn't apply to :class:`timedelta`
- objects.
- Subclass relationships::
- object
- timedelta
- tzinfo
- time
- date
- datetime
- .. _datetime-timedelta:
- :class:`timedelta` Objects
- --------------------------
- A :class:`timedelta` object represents a duration, the difference between two
- dates or times.
- .. class:: timedelta([days[, seconds[, microseconds[, milliseconds[, minutes[, hours[, weeks]]]]]]])
- All arguments are optional and default to ``0``. Arguments may be ints, longs,
- or floats, and may be positive or negative.
- Only *days*, *seconds* and *microseconds* are stored internally. Arguments are
- converted to those units:
- * A millisecond is converted to 1000 microseconds.
- * A minute is converted to 60 seconds.
- * An hour is converted to 3600 seconds.
- * A week is converted to 7 days.
- and days, seconds and microseconds are then normalized so that the
- representation is unique, with
- * ``0 <= microseconds < 1000000``
- * ``0 <= seconds < 3600*24`` (the number of seconds in one day)
- * ``-999999999 <= days <= 999999999``
- If any argument is a float and there are fractional microseconds, the fractional
- microseconds left over from all arguments are combined and their sum is rounded
- to the nearest microsecond. If no argument is a float, the conversion and
- normalization processes are exact (no information is lost).
- If the normalized value of days lies outside the indicated range,
- :exc:`OverflowError` is raised.
- Note that normalization of negative values may be surprising at first. For
- example,
- >>> from datetime import timedelta
- >>> d = timedelta(microseconds=-1)
- >>> (d.days, d.seconds, d.microseconds)
- (-1, 86399, 999999)
- Class attributes are:
- .. attribute:: timedelta.min
- The most negative :class:`timedelta` object, ``timedelta(-999999999)``.
- .. attribute:: timedelta.max
- The most positive :class:`timedelta` object, ``timedelta(days=999999999,
- hours=23, minutes=59, seconds=59, microseconds=999999)``.
- .. attribute:: timedelta.resolution
- The smallest possible difference between non-equal :class:`timedelta` objects,
- ``timedelta(microseconds=1)``.
- Note that, because of normalization, ``timedelta.max`` > ``-timedelta.min``.
- ``-timedelta.max`` is not representable as a :class:`timedelta` object.
- Instance attributes (read-only):
- +------------------+--------------------------------------------+
- | Attribute | Value |
- +==================+============================================+
- | ``days`` | Between -999999999 and 999999999 inclusive |
- +------------------+--------------------------------------------+
- | ``seconds`` | Between 0 and 86399 inclusive |
- +------------------+--------------------------------------------+
- | ``microseconds`` | Between 0 and 999999 inclusive |
- +------------------+--------------------------------------------+
- Supported operations:
- .. XXX this table is too wide!
- +--------------------------------+-----------------------------------------------+
- | Operation | Result |
- +================================+===============================================+
- | ``t1 = t2 + t3`` | Sum of *t2* and *t3*. Afterwards *t1*-*t2* == |
- | | *t3* and *t1*-*t3* == *t2* are true. (1) |
- +--------------------------------+-----------------------------------------------+
- | ``t1 = t2 - t3`` | Difference of *t2* and *t3*. Afterwards *t1* |
- | | == *t2* - *t3* and *t2* == *t1* + *t3* are |
- | | true. (1) |
- +--------------------------------+-----------------------------------------------+
- | ``t1 = t2 * i or t1 = i * t2`` | Delta multiplied by an integer or long. |
- | | Afterwards *t1* // i == *t2* is true, |
- | | provided ``i != 0``. |
- +--------------------------------+-----------------------------------------------+
- | | In general, *t1* \* i == *t1* \* (i-1) + *t1* |
- | | is true. (1) |
- +--------------------------------+-----------------------------------------------+
- | ``t1 = t2 // i`` | The floor is computed and the remainder (if |
- | | any) is thrown away. (3) |
- +--------------------------------+-----------------------------------------------+
- | ``+t1`` | Returns a :class:`timedelta` object with the |
- | | same value. (2) |
- +--------------------------------+-----------------------------------------------+
- | ``-t1`` | equivalent to :class:`timedelta`\ |
- | | (-*t1.days*, -*t1.seconds*, |
- | | -*t1.microseconds*), and to *t1*\* -1. (1)(4) |
- +--------------------------------+-----------------------------------------------+
- | ``abs(t)`` | equivalent to +*t* when ``t.days >= 0``, and |
- | | to -*t* when ``t.days < 0``. (2) |
- +--------------------------------+-----------------------------------------------+
- Notes:
- (1)
- This is exact, but may overflow.
- (2)
- This is exact, and cannot overflow.
- (3)
- Division by 0 raises :exc:`ZeroDivisionError`.
- (4)
- -*timedelta.max* is not representable as a :class:`timedelta` object.
- In addition to the operations listed above :class:`timedelta` objects support
- certain additions and subtractions with :class:`date` and :class:`datetime`
- objects (see below).
- Comparisons of :class:`timedelta` objects are supported with the
- :class:`timedelta` object representing the smaller duration considered to be the
- smaller timedelta. In order to stop mixed-type comparisons from falling back to
- the default comparison by object address, when a :class:`timedelta` object is
- compared to an object of a different type, :exc:`TypeError` is raised unless the
- comparison is ``==`` or ``!=``. The latter cases return :const:`False` or
- :const:`True`, respectively.
- :class:`timedelta` objects are :term:`hashable` (usable as dictionary keys), support
- efficient pickling, and in Boolean contexts, a :class:`timedelta` object is
- considered to be true if and only if it isn't equal to ``timedelta(0)``.
- Example usage:
- >>> from datetime import timedelta
- >>> year = timedelta(days=365)
- >>> another_year = timedelta(weeks=40, days=84, hours=23,
- ... minutes=50, seconds=600) # adds up to 365 days
- >>> year == another_year
- True
- >>> ten_years = 10 * year
- >>> ten_years, ten_years.days // 365
- (datetime.timedelta(3650), 10)
- >>> nine_years = ten_years - year
- >>> nine_years, nine_years.days // 365
- (datetime.timedelta(3285), 9)
- >>> three_years = nine_years // 3;
- >>> three_years, three_years.days // 365
- (datetime.timedelta(1095), 3)
- >>> abs(three_years - ten_years) == 2 * three_years + year
- True
- .. _datetime-date:
- :class:`date` Objects
- ---------------------
- A :class:`date` object represents a date (year, month and day) in an idealized
- calendar, the current Gregorian calendar indefinitely extended in both
- directions. January 1 of year 1 is called day number 1, January 2 of year 1 is
- called day number 2, and so on. This matches the definition of the "proleptic
- Gregorian" calendar in Dershowitz and Reingold's book Calendrical Calculations,
- where it's the base calendar for all computations. See the book for algorithms
- for converting between proleptic Gregorian ordinals and many other calendar
- systems.
- .. class:: date(year, month, day)
- All arguments are required. Arguments may be ints or longs, in the following
- ranges:
- * ``MINYEAR <= year <= MAXYEAR``
- * ``1 <= month <= 12``
- * ``1 <= day <= number of days in the given month and year``
- If an argument outside those ranges is given, :exc:`ValueError` is raised.
- Other constructors, all class methods:
- .. method:: date.today()
- Return the current local date. This is equivalent to
- ``date.fromtimestamp(time.time())``.
- .. method:: date.fromtimestamp(timestamp)
- Return the local date corresponding to the POSIX timestamp, such as is returned
- by :func:`time.time`. This may raise :exc:`ValueError`, if the timestamp is out
- of the range of values supported by the platform C :cfunc:`localtime` function.
- It's common for this to be restricted to years from 1970 through 2038. Note
- that on non-POSIX systems that include leap seconds in their notion of a
- timestamp, leap seconds are ignored by :meth:`fromtimestamp`.
- .. method:: date.fromordinal(ordinal)
- Return the date corresponding to the proleptic Gregorian ordinal, where January
- 1 of year 1 has ordinal 1. :exc:`ValueError` is raised unless ``1 <= ordinal <=
- date.max.toordinal()``. For any date *d*, ``date.fromordinal(d.toordinal()) ==
- d``.
- Class attributes:
- .. attribute:: date.min
- The earliest representable date, ``date(MINYEAR, 1, 1)``.
- .. attribute:: date.max
- The latest representable date, ``date(MAXYEAR, 12, 31)``.
- .. attribute:: date.resolution
- The smallest possible difference between non-equal date objects,
- ``timedelta(days=1)``.
- Instance attributes (read-only):
- .. attribute:: date.year
- Between :const:`MINYEAR` and :const:`MAXYEAR` inclusive.
- .. attribute:: date.month
- Between 1 and 12 inclusive.
- .. attribute:: date.day
- Between 1 and the number of days in the given month of the given year.
- Supported operations:
- +-------------------------------+----------------------------------------------+
- | Operation | Result |
- +===============================+==============================================+
- | ``date2 = date1 + timedelta`` | *date2* is ``timedelta.days`` days removed |
- | | from *date1*. (1) |
- +-------------------------------+----------------------------------------------+
- | ``date2 = date1 - timedelta`` | Computes *date2* such that ``date2 + |
- | | timedelta == date1``. (2) |
- +-------------------------------+----------------------------------------------+
- | ``timedelta = date1 - date2`` | \(3) |
- +-------------------------------+----------------------------------------------+
- | ``date1 < date2`` | *date1* is considered less than *date2* when |
- | | *date1* precedes *date2* in time. (4) |
- +-------------------------------+----------------------------------------------+
- Notes:
- (1)
- *date2* is moved forward in time if ``timedelta.days > 0``, or backward if
- ``timedelta.days < 0``. Afterward ``date2 - date1 == timedelta.days``.
- ``timedelta.seconds`` and ``timedelta.microseconds`` are ignored.
- :exc:`OverflowError` is raised if ``date2.year`` would be smaller than
- :const:`MINYEAR` or larger than :const:`MAXYEAR`.
- (2)
- This isn't quite equivalent to date1 + (-timedelta), because -timedelta in
- isolation can overflow in cases where date1 - timedelta does not.
- ``timedelta.seconds`` and ``timedelta.microseconds`` are ignored.
- (3)
- This is exact, and cannot overflow. timedelta.seconds and
- timedelta.microseconds are 0, and date2 + timedelta == date1 after.
- (4)
- In other words, ``date1 < date2`` if and only if ``date1.toordinal() <
- date2.toordinal()``. In order to stop comparison from falling back to the
- default scheme of comparing object addresses, date comparison normally raises
- :exc:`TypeError` if the other comparand isn't also a :class:`date` object.
- However, ``NotImplemented`` is returned instead if the other comparand has a
- :meth:`timetuple` attribute. This hook gives other kinds of date objects a
- chance at implementing mixed-type comparison. If not, when a :class:`date`
- object is compared to an object of a different type, :exc:`TypeError` is raised
- unless the comparison is ``==`` or ``!=``. The latter cases return
- :const:`False` or :const:`True`, respectively.
- Dates can be used as dictionary keys. In Boolean contexts, all :class:`date`
- objects are considered to be true.
- Instance methods:
- .. method:: date.replace(year, month, day)
- Return a date with the same value, except for those members given new values by
- whichever keyword arguments are specified. For example, if ``d == date(2002,
- 12, 31)``, then ``d.replace(day=26) == date(2002, 12, 26)``.
- .. method:: date.timetuple()
- Return a :class:`time.struct_time` such as returned by :func:`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(), d.toordinal() - date(d.year, 1, 1).toordinal() + 1, -1))``
- .. method:: date.toordinal()
- Return the proleptic Gregorian ordinal of the date, where January 1 of year 1
- has ordinal 1. For any :class:`date` object *d*,
- ``date.fromordinal(d.toordinal()) == d``.
- .. method:: date.weekday()
- Return the day of the week as an integer, where Monday is 0 and Sunday is 6.
- For example, ``date(2002, 12, 4).weekday() == 2``, a Wednesday. See also
- :meth:`isoweekday`.
- .. method:: date.isoweekday()
- Return the day of the week as an integer, where Monday is 1 and Sunday is 7.
- For example, ``date(2002, 12, 4).isoweekday() == 3``, a Wednesday. See also
- :meth:`weekday`, :meth:`isocalendar`.
- .. method:: date.isocalendar()
- Return a 3-tuple, (ISO year, ISO week number, ISO weekday).
- The ISO calendar is a widely used variant of the Gregorian calendar. See
- http://www.phys.uu.nl/ vgent/calendar/isocalendar.htm for a good explanation.
- The ISO year consists of 52 or 53 full weeks, and where a week starts on a
- Monday and ends on a Sunday. The first week of an ISO year is the first
- (Gregorian) calendar week of a year containing a Thursday. This is called week
- number 1, and the ISO year of that Thursday is the same as its Gregorian year.
- For example, 2004 begins on a Thursday, so the first week of ISO year 2004
- begins on Monday, 29 Dec 2003 and ends on Sunday, 4 Jan 2004, so that
- ``date(2003, 12, 29).isocalendar() == (2004, 1, 1)`` and ``date(2004, 1,
- 4).isocalendar() == (2004, 1, 7)``.
- .. method:: 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'``.
- .. method:: date.__str__()
- For a date *d*, ``str(d)`` is equivalent to ``d.isoformat()``.
- .. method:: date.ctime()
- Return a string representing the date, for example ``date(2002, 12,
- 4).ctime() == 'Wed Dec 4 00:00:00 2002'``. ``d.ctime()`` is equivalent to
- ``time.ctime(time.mktime(d.timetuple()))`` on platforms where the native C
- :cfunc:`ctime` function (which :func:`time.ctime` invokes, but which
- :meth:`date.ctime` does not invoke) conforms to the C standard.
- .. method:: date.strftime(format)
- Return a string representing the date, controlled by an explicit format string.
- Format codes referring to hours, minutes or seconds will see 0 values. See
- section :ref:`strftime-behavior`.
- Example of counting days to an event::
- >>> import time
- >>> from datetime import date
- >>> today = date.today()
- >>> today
- datetime.date(2007, 12, 5)
- >>> today == date.fromtimestamp(time.time())
- True
- >>> my_birthday = date(today.year, 6, 24)
- >>> if my_birthday < today:
- ... my_birthday = my_birthday.replace(year=today.year + 1)
- >>> my_birthday
- datetime.date(2008, 6, 24)
- >>> time_to_birthday = abs(my_birthday - today)
- >>> time_to_birthday.days
- 202
- Example of working with :class:`date`:
- .. doctest::
- >>> 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: # doctest: +SKIP
- ... 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: # doctest: +SKIP
- ... 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'
- .. _datetime-datetime:
- :class:`datetime` Objects
- -------------------------
- A :class:`datetime` object is a single object containing all the information
- from a :class:`date` object and a :class:`time` object. Like a :class:`date`
- object, :class:`datetime` assumes the current Gregorian calendar extended in
- both directions; like a time object, :class:`datetime` assumes there are exactly
- 3600\*24 seconds in every day.
- Constructor:
- .. class:: datetime(year, month, day[, hour[, minute[, second[, microsecond[, tzinfo]]]]])
- The year, month and day arguments are required. *tzinfo* may be ``None``, or an
- instance of a :class:`tzinfo` subclass. The remaining arguments may be ints or
- longs, in the following ranges:
- * ``MINYEAR <= year <= MAXYEAR``
- * ``1 <= month <= 12``
- * ``1 <= day <= number of days in the given month and year``
- * ``0 <= hour < 24``
- * ``0 <= minute < 60``
- * ``0 <= second < 60``
- * ``0 <= microsecond < 1000000``
- If an argument outside those ranges is given, :exc:`ValueError` is raised.
- Other constructors, all class methods:
- .. method:: datetime.today()
- Return the current local datetime, with :attr:`tzinfo` ``None``. This is
- equivalent to ``datetime.fromtimestamp(time.time())``. See also :meth:`now`,
- :meth:`fromtimestamp`.
- .. method:: datetime.now([tz])
- Return the current local date and time. If optional argument *tz* is ``None``
- or not specified, this is like :meth:`today`, but, if possible, supplies more
- precision than can be gotten from going through a :func:`time.time` timestamp
- (for example, this may be possible on platforms supplying the C
- :cfunc:`gettimeofday` function).
- Else *tz* must be an instance of a class :class:`tzinfo` subclass, and the
- current date and time are converted to *tz*'s time zone. In this case the
- result is equivalent to ``tz.fromutc(datetime.utcnow().replace(tzinfo=tz))``.
- See also :meth:`today`, :meth:`utcnow`.
- .. method:: datetime.utcnow()
- Return the current UTC date and time, with :attr:`tzinfo` ``None``. This is like
- :meth:`now`, but returns the current UTC date and time, as a naive
- :class:`datetime` object. See also :meth:`now`.
- .. method:: datetime.fromtimestamp(timestamp[, tz])
- Return the local date and time corresponding to the POSIX timestamp, such as is
- returned by :func:`time.time`. If optional argument *tz* is ``None`` or not
- specified, the timestamp is converted to the platform's local date and time, and
- the returned :class:`datetime` object is naive.
- Else *tz* must be an instance of a class :class:`tzinfo` subclass, and the
- timestamp is converted to *tz*'s time zone. In this case the result is
- equivalent to
- ``tz.fromutc(datetime.utcfromtimestamp(timestamp).replace(tzinfo=tz))``.
- :meth:`fromtimestamp` may raise :exc:`ValueError`, if the timestamp is out of
- the range of values supported by the platform C :cfunc:`localtime` or
- :cfunc:`gmtime` functions. It's common for this to be restricted to years in
- 1970 through 2038. Note that on non-POSIX systems that include leap seconds in
- their notion of a timestamp, leap seconds are ignored by :meth:`fromtimestamp`,
- and then it's possible to have two timestamps differing by a second that yield
- identical :class:`datetime` objects. See also :meth:`utcfromtimestamp`.
- .. method:: datetime.utcfromtimestamp(timestamp)
- Return the UTC :class:`datetime` corresponding to the POSIX timestamp, with
- :attr:`tzinfo` ``None``. This may raise :exc:`ValueError`, if the timestamp is
- out of the range of values supported by the platform C :cfunc:`gmtime` function.
- It's common for this to be restricted to years in 1970 through 2038. See also
- :meth:`fromtimestamp`.
- .. method:: datetime.fromordinal(ordinal)
- Return the :class:`datetime` corresponding to the proleptic Gregorian ordinal,
- where January 1 of year 1 has ordinal 1. :exc:`ValueError` is raised unless ``1
- <= ordinal <= datetime.max.toordinal()``. The hour, minute, second and
- microsecond of the result are all 0, and :attr:`tzinfo` is ``None``.
- .. method:: datetime.combine(date, time)
- Return a new :class:`datetime` object whose date members are equal to the given
- :class:`date` object's, and whose time and :attr:`tzinfo` members are equal to
- the given :class:`time` object's. For any :class:`datetime` object *d*, ``d ==
- datetime.combine(d.date(), d.timetz())``. If date is a :class:`datetime`
- object, its time and :attr:`tzinfo` members are ignored.
- .. method:: datetime.strptime(date_string, format)
- Return a :class:`datetime` corresponding to *date_string*, parsed according to
- *format*. This is equivalent to ``datetime(*(time.strptime(date_string,
- format)[0:6]))``. :exc:`ValueError` is raised if the date_string and format
- can't be parsed by :func:`time.strptime` or if it returns a value which isn't a
- time tuple.
- .. versionadded:: 2.5
- Class attributes:
- .. attribute:: datetime.min
- The earliest representable :class:`datetime`, ``datetime(MINYEAR, 1, 1,
- tzinfo=None)``.
- .. attribute:: datetime.max
- The latest representable :class:`datetime`, ``datetime(MAXYEAR, 12, 31, 23, 59,
- 59, 999999, tzinfo=None)``.
- .. attribute:: datetime.resolution
- The smallest possible difference between non-equal :class:`datetime` objects,
- ``timedelta(microseconds=1)``.
- Instance attributes (read-only):
- .. attribute:: datetime.year
- Between :const:`MINYEAR` and :const:`MAXYEAR` inclusive.
- .. attribute:: datetime.month
- Between 1 and 12 inclusive.
- .. attribute:: datetime.day
- Between 1 and the number of days in the given month of the given year.
- .. attribute:: datetime.hour
- In ``range(24)``.
- .. attribute:: datetime.minute
- In ``range(60)``.
- .. attribute:: datetime.second
- In ``range(60)``.
- .. attribute:: datetime.microsecond
- In ``range(1000000)``.
- .. attribute:: datetime.tzinfo
- The object passed as the *tzinfo* argument to the :class:`datetime` constructor,
- or ``None`` if none was passed.
- Supported operations:
- +---------------------------------------+-------------------------------+
- | Operation | Result |
- +=======================================+===============================+
- | ``datetime2 = datetime1 + timedelta`` | \(1) |
- +---------------------------------------+-------------------------------+
- | ``datetime2 = datetime1 - timedelta`` | \(2) |
- +---------------------------------------+-------------------------------+
- | ``timedelta = datetime1 - datetime2`` | \(3) |
- +---------------------------------------+-------------------------------+
- | ``datetime1 < datetime2`` | Compares :class:`datetime` to |
- | | :class:`datetime`. (4) |
- +---------------------------------------+-------------------------------+
- (1)
- datetime2 is a duration of timedelta removed from datetime1, moving forward in
- time if ``timedelta.days`` > 0, or backward if ``timedelta.days`` < 0. The
- result has the same :attr:`tzinfo` member as the input datetime, and datetime2 -
- datetime1 == timedelta after. :exc:`OverflowError` is raised if datetime2.year
- would be smaller than :const:`MINYEAR` or larger than :const:`MAXYEAR`. Note
- that no time zone adjustments are done even if the input is an aware object.
- (2)
- Computes the datetime2 such that datetime2 + timedelta == datetime1. As for
- addition, the result has the same :attr:`tzinfo` member as the input datetime,
- and no time zone adjustments are done even if the input is aware. This isn't
- quite equivalent to datetime1 + (-timedelta), because -timedelta in isolation
- can overflow in cases where datetime1 - timedelta does not.
- (3)
- Subtraction of a :class:`datetime` from a :class:`datetime` is defined only if
- both operands are naive, or if both are aware. If one is aware and the other is
- naive, :exc:`TypeError` is raised.
- If both are naive, or both are aware and have the same :attr:`tzinfo` member,
- the :attr:`tzinfo` members are ignored, and the result is a :class:`timedelta`
- object *t* such that ``datetime2 + t == datetime1``. No time zone adjustments
- are done in this case.
- If both are aware and have different :attr:`tzinfo` members, ``a-b`` acts as if
- *a* and *b* were first converted to naive UTC datetimes first. The result is
- ``(a.replace(tzinfo=None) - a.utcoffset()) - (b.replace(tzinfo=None) -
- b.utcoffset())`` except that the implementation never overflows.
- (4)
- *datetime1* is considered less than *datetime2* when *datetime1* precedes
- *datetime2* in time.
- If one comparand is naive and the other is aware, :exc:`TypeError` is raised.
- If both comparands are aware, and have the same :attr:`tzinfo` member, the
- common :attr:`tzinfo` member is ignored and the base datetimes are compared. If
- both comparands are aware and have different :attr:`tzinfo` members, the
- comparands are first adjusted by subtracting their UTC offsets (obtained from
- ``self.utcoffset()``).
- .. note::
- In order to stop comparison from falling back to the default scheme of comparing
- object addresses, datetime comparison normally raises :exc:`TypeError` if the
- other comparand isn't also a :class:`datetime` object. However,
- ``NotImplemented`` is returned instead if the other comparand has a
- :meth:`timetuple` attribute. This hook gives other kinds of date objects a
- chance at implementing mixed-type comparison. If not, when a :class:`datetime`
- object is compared to an object of a different type, :exc:`TypeError` is raised
- unless the comparison is ``==`` or ``!=``. The latter cases return
- :const:`False` or :const:`True`, respectively.
- :class:`datetime` objects can be used as dictionary keys. In Boolean contexts,
- all :class:`datetime` objects are considered to be true.
- Instance methods:
- .. method:: datetime.date()
- Return :class:`date` object with same year, month and day.
- .. method:: datetime.time()
- Return :class:`time` object with same hour, minute, second and microsecond.
- :attr:`tzinfo` is ``None``. See also method :meth:`timetz`.
- .. method:: datetime.timetz()
- Return :class:`time` object with same hour, minute, second, microsecond, and
- tzinfo members. See also method :meth:`time`.
- .. method:: datetime.replace([year[, month[, day[, hour[, minute[, second[, microsecond[, tzinfo]]]]]]]])
- Return a datetime with the same members, except for those members given new
- values by whichever keyword arguments are specified. Note that ``tzinfo=None``
- can be specified to create a naive datetime from an aware datetime with no
- conversion of date and time members.
- .. method:: datetime.astimezone(tz)
- Return a :class:`datetime` object with new :attr:`tzinfo` member *tz*, adjusting
- the date and time members so the result is the same UTC time as *self*, but in
- *tz*'s local time.
- *tz* must be an instance of a :class:`tzinfo` subclass, and its
- :meth:`utcoffset` and :meth:`dst` methods must not return ``None``. *self* must
- be aware (``self.tzinfo`` must not be ``None``, and ``self.utcoffset()`` must
- not return ``None``).
- If ``self.tzinfo`` is *tz*, ``self.astimezone(tz)`` is equal to *self*: no
- adjustment of date or time members is performed. Else the result is local time
- in time zone *tz*, representing the same UTC time as *self*: after ``astz =
- dt.astimezone(tz)``, ``astz - astz.utcoffset()`` will usually have the same date
- and time members as ``dt - dt.utcoffset()``. The discussion of class
- :class:`tzinfo` explains the cases at Daylight Saving Time transition boundaries
- where this cannot be achieved (an issue only if *tz* models both standard and
- daylight time).
- If you merely want to attach a time zone object *tz* to a datetime *dt* without
- adjustment of date and time members, use ``dt.replace(tzinfo=tz)``. If you
- merely want to remove the time zone object from an aware datetime *dt* without
- conversion of date and time members, use ``dt.replace(tzinfo=None)``.
- Note that the default :meth:`tzinfo.fromutc` method can be overridden in a
- :class:`tzinfo` subclass to affect the result returned by :meth:`astimezone`.
- Ignoring error cases, :meth:`astimezone` acts like::
- def astimezone(self, tz):
- if self.tzinfo is tz:
- return self
- # Convert self to UTC, and attach the new time zone object.
- utc = (self - self.utcoffset()).replace(tzinfo=tz)
- # Convert from UTC to tz's local time.
- return tz.fromutc(utc)
- .. method:: datetime.utcoffset()
- If :attr:`tzinfo` is ``None``, returns ``None``, else returns
- ``self.tzinfo.utcoffset(self)``, and raises an exception if the latter doesn't
- return ``None``, or a :class:`timedelta` object representing a whole number of
- minutes with magnitude less than one day.
- .. method:: datetime.dst()
- If :attr:`tzinfo` is ``None``, returns ``None``, else returns
- ``self.tzinfo.dst(self)``, and raises an exception if the latter doesn't return
- ``None``, or a :class:`timedelta` object representing a whole number of minutes
- with magnitude less than one day.
- .. method:: datetime.tzname()
- If :attr:`tzinfo` is ``None``, returns ``None``, else returns
- ``self.tzinfo.tzname(self)``, raises an exception if the latter doesn't return
- ``None`` or a string object,
- .. method:: datetime.timetuple()
- Return a :class:`time.struct_time` such as returned by :func:`time.localtime`.
- ``d.timetuple()`` is equivalent to ``time.struct_time((d.year, d.month, d.day,
- d.hour, d.minute, d.second, d.weekday(), d.toordinal() - date(d.year, 1,
- 1).toordinal() + 1, dst))`` The :attr:`tm_isdst` flag of the result is set
- according to the :meth:`dst` method: :attr:`tzinfo` is ``None`` or :meth:`dst`
- returns ``None``, :attr:`tm_isdst` is set to ``-1``; else if :meth:`dst`
- returns a non-zero value, :attr:`tm_isdst` is set to ``1``; else ``tm_isdst`` is
- set to ``0``.
- .. method:: datetime.utctimetuple()
- If :class:`datetime` instance *d* is naive, this is the same as
- ``d.timetuple()`` except that :attr:`tm_isdst` is forced to 0 regardless of what
- ``d.dst()`` returns. DST is never in effect for a UTC time.
- If *d* is aware, *d* is normalized to UTC time, by subtracting
- ``d.utcoffset()``, and a :class:`time.struct_time` for the normalized time is
- returned. :attr:`tm_isdst` is forced to 0. Note that the result's
- :attr:`tm_year` member may be :const:`MINYEAR`\ -1 or :const:`MAXYEAR`\ +1, if
- *d*.year was ``MINYEAR`` or ``MAXYEAR`` and UTC adjustment spills over a year
- boundary.
- .. method:: datetime.toordinal()
- Return the proleptic Gregorian ordinal of the date. The same as
- ``self.date().toordinal()``.
- .. method:: datetime.weekday()
- Return the day of the week as an integer, where Monday is 0 and Sunday is 6.
- The same as ``self.date().weekday()``. See also :meth:`isoweekday`.
- .. method:: datetime.isoweekday()
- Return the day of the week as an integer, where Monday is 1 and Sunday is 7.
- The same as ``self.date().isoweekday()``. See also :meth:`weekday`,
- :meth:`isocalendar`.
- .. method:: datetime.isocalendar()
- Return a 3-tuple, (ISO year, ISO week number, ISO weekday). The same as
- ``self.date().isocalendar()``.
- .. method:: datetime.isoformat([sep])
- Return a string representing the date and time in ISO 8601 format,
- YYYY-MM-DDTHH:MM:SS.mmmmmm or, if :attr:`microsecond` is 0,
- YYYY-MM-DDTHH:MM:SS
- If :meth:`utcoffset` does not return ``None``, a 6-character string is
- appended, giving the UTC offset in (signed) hours and minutes:
- YYYY-MM-DDTHH:MM:SS.mmmmmm+HH:MM or, if :attr:`microsecond` is 0
- YYYY-MM-DDTHH:MM:SS+HH:MM
- The optional argument *sep* (default ``'T'``) is a one-character separator,
- placed between the date and time portions of the result. For example,
- >>> from datetime import tzinfo, timedelta, datetime
- >>> class TZ(tzinfo):
- ... def utcoffset(self, dt): return timedelta(minutes=-399)
- ...
- >>> datetime(2002, 12, 25, tzinfo=TZ()).isoformat(' ')
- '2002-12-25 00:00:00-06:39'
- .. method:: datetime.__str__()
- For a :class:`datetime` instance *d*, ``str(d)`` is equivalent to
- ``d.isoformat(' ')``.
- .. method:: datetime.ctime()
- Return a string representing the date and time, for example ``datetime(2002, 12,
- 4, 20, 30, 40).ctime() == 'Wed Dec 4 20:30:40 2002'``. ``d.ctime()`` is
- equivalent to ``time.ctime(time.mktime(d.timetuple()))`` on platforms where the
- native C :cfunc:`ctime` function (which :func:`time.ctime` invokes, but which
- :meth:`datetime.ctime` does not invoke) conforms to the C standard.
- .. method:: datetime.strftime(format)
- Return a string representing the date and time, controlled by an explicit format
- string. See section :ref:`strftime-behavior`.
- Examples of working with datetime objects:
- .. doctest::
- >>> 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() # doctest: +SKIP
- datetime.datetime(2007, 12, 6, 16, 29, 43, 79043) # GMT +1
- >>> datetime.utcnow() # doctest: +SKIP
- 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: # doctest: +SKIP
- ... 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: # doctest: +SKIP
- ... 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'
- Using datetime with tzinfo:
- >>> from datetime import timedelta, datetime, tzinfo
- >>> class GMT1(tzinfo):
- ... def __init__(self): # 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)
- ... def utcoffset(self, dt):
- ... return timedelta(hours=1) + self.dst(dt)
- ... def dst(self, dt):
- ... 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 __init__(self):
- ... 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)
- ... def utcoffset(self, dt):
- ... return timedelta(hours=1) + self.dst(dt)
- ... def dst(self, dt):
- ... if self.dston <= dt.replace(tzinfo=None) < self.dstoff:
- ... return timedelta(hours=2)
- ... 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 # doctest: +ELLIPSIS
- datetime.datetime(2006, 6, 14, 14, 0, tzinfo=<GMT2 object at 0x...>)
- >>> dt2 # doctest: +ELLIPSIS
- datetime.datetime(2006, 6, 14, 13, 0, tzinfo=<GMT1 object at 0x...>)
- >>> dt2.utctimetuple() == dt3.utctimetuple()
- True
- .. _datetime-time:
- :class:`time` Objects
- ---------------------
- A time object represents a (local) time of day, independent of any particular
- day, and subject to adjustment via a :class:`tzinfo` object.
- .. class:: time(hour[, minute[, second[, microsecond[, tzinfo]]]])
- All arguments are optional. *tzinfo* may be ``None``, or an instance of a
- :class:`tzinfo` subclass. The remaining arguments may be ints or longs, in the
- following ranges:
- * ``0 <= hour < 24``
- * ``0 <= minute < 60``
- * ``0 <= second < 60``
- * ``0 <= microsecond < 1000000``.
- If an argument outside those ranges is given, :exc:`ValueError` is raised. All
- default to ``0`` except *tzinfo*, which defaults to :const:`None`.
- Class attributes:
- .. attribute:: time.min
- The earliest representable :class:`time`, ``time(0, 0, 0, 0)``.
- .. attribute:: time.max
- The latest representable :class:`time`, ``time(23, 59, 59, 999999)``.
- .. attribute:: time.resolution
- The smallest possible difference between non-equal :class:`time` objects,
- ``timedelta(microseconds=1)``, although note that arithmetic on :class:`time`
- objects is not supported.
- Instance attributes (read-only):
- .. attribute:: time.hour
- In ``range(24)``.
- .. attribute:: time.minute
- In ``range(60)``.
- .. attribute:: time.second
- In ``range(60)``.
- .. attribute:: time.microsecond
- In ``range(1000000)``.
- .. attribute:: time.tzinfo
- The object passed as the tzinfo argument to the :class:`time` constructor, or
- ``None`` if none was passed.
- Supported operations:
- * comparison of :class:`time` to :class:`time`, where *a* is considered less
- than *b* when *a* precedes *b* in time. If one comparand is naive and the other
- is aware, :exc:`TypeError` is raised. If both comparands are aware, and have
- the same :attr:`tzinfo` member, the common :attr:`tzinfo` member is ignored and
- the base times are compared. If both comparands are aware and have different
- :attr:`tzinfo` members, the comparands are first adjusted by subtracting their
- UTC offsets (obtained from ``self.utcoffset()``). In order to stop mixed-type
- comparisons from falling back to the default comparison by object address, when
- a :class:`time` object is compared to an object of a different type,
- :exc:`TypeError` is raised unless the comparison is ``==`` or ``!=``. The
- latter cases return :const:`False` or :const:`True`, respectively.
- * hash, use as dict key
- * efficient pickling
- * in Boolean contexts, a :class:`time` object is considered to be true if and
- only if, after converting it to minutes and subtracting :meth:`utcoffset` (or
- ``0`` if that's ``None``), the result is non-zero.
- Instance methods:
- .. method:: time.replace([hour[, minute[, second[, microsecond[, tzinfo]]]]])
- Return a :class:`time` with the same value, except for those members given new
- values by whichever keyword arguments are specified. Note that ``tzinfo=None``
- can be specified to create a naive :class:`time` from an aware :class:`time`,
- without conversion of the time members.
- .. method:: time.isoformat()
- Return a string representing the time in ISO 8601 format, HH:MM:SS.mmmmmm or, if
- self.microsecond is 0, HH:MM:SS If :meth:`utcoffset` does not return ``None``, a
- 6-character string is appended, giving the UTC offset in (signed) hours and
- minutes: HH:MM:SS.mmmmmm+HH:MM or, if self.microsecond is 0, HH:MM:SS+HH:MM
- .. method:: time.__str__()
- For a time *t*, ``str(t)`` is equivalent to ``t.isoformat()``.
- .. method:: time.strftime(format)
- Return a string representing the time, controlled by an explicit format string.
- See section :ref:`strftime-behavior`.
- .. method:: time.utcoffset()
- If :attr:`tzinfo` is ``None``, returns ``None``, else returns
- ``self.tzinfo.utcoffset(None)``, and raises an exception if the latter doesn't
- return ``None`` or a :class:`timedelta` object representing a whole number of
- minutes with magnitude less than one day.
- .. method:: time.dst()
- If :attr:`tzinfo` is ``None``, returns ``None``, else returns
- ``self.tzinfo.dst(None)``, and raises an exception if the latter doesn't return
- ``None``, or a :class:`timedelta` object representing a whole number of minutes
- with magnitude less than one day.
- .. method:: time.tzname()
- If :attr:`tzinfo` is ``None``, returns ``None``, else returns
- ``self.tzinfo.tzname(None)``, or raises an exception if the latter doesn't
- return ``None`` or a string object.
- Example:
- >>> from datetime import time, tzinfo
- >>> class GMT1(tzinfo):
- ... def utcoffset(self, dt):
- ... return timedelta(hours=1)
- ... def dst(self, dt):
- ... return timedelta(0)
- ... def tzname(self,dt):
- ... return "Europe/Prague"
- ...
- >>> t = time(12, 10, 30, tzinfo=GMT1())
- >>> t # doctest: +ELLIPSIS
- datetime.time(12, 10, 30, tzinfo=<GMT1 object at 0x...>)
- >>> gmt = GMT1()
- >>> t.isoformat()
- '12:10:30+01:00'
- >>> t.dst()
- datetime.timedelta(0)
- >>> t.tzname()
- 'Europe/Prague'
- >>> t.strftime("%H:%M:%S %Z")
- '12:10:30 Europe/Prague'
- .. _datetime-tzinfo:
- :class:`tzinfo` Objects
- -----------------------
- :class:`tzinfo` is an abstract base class, meaning that this class should not be
- instantiated directly. You need to derive a concrete subclass, and (at least)
- supply implementations of the standard :class:`tzinfo` methods needed by the
- :class:`datetime` methods you use. The :mod:`datetime` module does not supply
- any concrete subclasses of :class:`tzinfo`.
- An instance of (a concrete subclass of) :class:`tzinfo` can be passed to the
- constructors for :class:`datetime` and :class:`time` objects. The latter objects
- view their members as being in local time, and the :class:`tzinfo` object
- supports methods revealing offset of local time from UTC, the name of the time
- zone, and DST offset, all relative to a date or time object passed to them.
- Special requirement for pickling: A :class:`tzinfo` subclass must have an
- :meth:`__init__` method that can be called with no arguments, else it can be
- pickled but possibly not unpickled again. This is a technical requirement that
- may be relaxed in the future.
- A concrete subclass of :class:`tzinfo` may need to implement the following
- methods. Exactly which methods are needed depends on the uses made of aware
- :mod:`datetime` objects. If in doubt, simply implement all of them.
- .. method:: tzinfo.utcoffset(self, dt)
- Return offset of local time from UTC, in minutes east of UTC. If local time is
- west of UTC, this should be negative. Note that this is intended to be the
- total offset from UTC; for example, if a :class:`tzinfo` object represents both
- time zone and DST adjustments, :meth:`utcoffset` should return their sum. If
- the UTC offset isn't known, return ``None``. Else the value returned must be a
- :class:`timedelta` object specifying a whole number of minutes in the range
- -1439 to 1439 inclusive (1440 = 24\*60; the magnitude of the offset must be less
- than one day). Most implementations of :meth:`utcoffset` will probably look
- like one of these two::
- return CONSTANT # fixed-offset class
- return CONSTANT + self.dst(dt) # daylight-aware class
- If :meth:`utcoffset` does not return ``None``, :meth:`dst` should not return
- ``None`` either.
- The default implementation of :meth:`utcoffset` raises
- :exc:`NotImplementedError`.
- .. method:: tzinfo.dst(self, dt)
- Return the daylight saving time (DST) adjustment, in minutes east of UTC, or
- ``None`` if DST information isn't known. Return ``timedelta(0)`` if DST is not
- in effect. If DST is in effect, return the offset as a :class:`timedelta` object
- (see :meth:`utcoffset` for details). Note that DST offset, if applicable, has
- already been added to the UTC offset returned by :meth:`utcoffset`, so there's
- no need to consult :meth:`dst` unless you're interested in obtaining DST info
- separately. For example, :meth:`datetime.timetuple` calls its :attr:`tzinfo`
- member's :meth:`dst` method to determine how the :attr:`tm_isdst` flag should be
- set, and :meth:`tzinfo.fromutc` calls :meth:`dst` to account for DST changes
- when crossing time zones.
- An instance *tz* of a :class:`tzinfo` subclass that models both standard and
- daylight times must be consistent in this sense:
- ``tz.utcoffset(dt) - tz.dst(dt)``
- must return the same result for every :class:`datetime` *dt* with ``dt.tzinfo ==
- tz`` For sane :class:`tzinfo` subclasses, this expression yields the time
- zone's "standard offset", which should not depend on the date or the time, but
- only on geographic location. The implementation of :meth:`datetime.astimezone`
- relies on this, but cannot detect violations; it's the programmer's
- responsibility to ensure it. If a :class:`tzinfo` subclass cannot guarantee
- this, it may be able to override the default implementation of
- :meth:`tzinfo.fromutc` to work correctly with :meth:`astimezone` regardless.
- Most implementations of :meth:`dst` will probably look like one of these two::
- def dst(self):
- # a fixed-offset class: doesn't account for DST
- return timedelta(0)
- or ::
- def dst(self):
- # Code to set dston and dstoff to the time zone's DST
- # transition times based on the input dt.year, and expressed
- # in standard local time. Then
- if dston <= dt.replace(tzinfo=None) < dstoff:
- return timedelta(hours=1)
- else:
- return timedelta(0)
- The default implementation of :meth:`dst` raises :exc:`NotImplementedError`.
- .. method:: tzinfo.tzname(self, dt)
- Return the time zone name corresponding to the :class:`datetime` object *dt*, as
- a string. Nothing about string names is defined by the :mod:`datetime` module,
- and there's no requirement that it mean anything in particular. For example,
- "GMT", "UTC", "-500", "-5:00", "EDT", "US/Eastern", "America/New York" are all
- valid replies. Return ``None`` if a string name isn't known. Note that this is
- a method rather than a fixed string primarily because some :class:`tzinfo`
- subclasses will wish to return different names depending on the specific value
- of *dt* passed, especially if the :class:`tzinfo` class is accounting for
- daylight time.
- The default implementation of :meth:`tzname` raises :exc:`NotImplementedError`.
- These methods are called by a :class:`datetime` or :class:`time` object, in
- response to their methods of the same names. A :class:`datetime` object passes
- itself as the argument, and a :class:`time` object passes ``None`` as the
- argument. A :class:`tzinfo` subclass's methods should therefore be prepared to
- accept a *dt* argument of ``None``, or of class :class:`datetime`.
- When ``None`` is passed, it's up to the class designer to decide the best
- response. For example, returning ``None`` is appropriate if the class wishes to
- say that time objects don't participate in the :class:`tzinfo` protocols. It
- may be more useful for ``utcoffset(None)`` to return the standard UTC offset, as
- there is no other convention for discovering the standard offset.
- When a :class:`datetime` object is passed in response to a :class:`datetime`
- method, ``dt.tzinfo`` is the same object as *self*. :class:`tzinfo` methods can
- rely on this, unless user code calls :class:`tzinfo` methods directly. The
- intent is that the :class:`tzinfo` methods interpret *dt* as being in local
- time, and not need worry about objects in other timezones.
- There is one more :class:`tzinfo` method that a subclass may wish to override:
- .. method:: tzinfo.fromutc(self, dt)
- This is called from the default :class:`datetime.astimezone()` implementation.
- When called from that, ``dt.tzinfo`` is *self*, and *dt*'s date and time members
- are to be viewed as expressing a UTC time. The purpose of :meth:`fromutc` is to
- adjust the date and time members, returning an equivalent datetime in *self*'s
- local time.
- Most :class:`tzinfo` subclasses should be able to inherit the default
- :meth:`fromutc` implementation without problems. It's strong enough to handle
- fixed-offset time zones, and time zones accounting for both standard and
- daylight time, and the latter even if the DST transition times differ in
- different years. An example of a time zone the default :meth:`fromutc`
- implementation may not handle correctly in all cases is one where the standard
- offset (from UTC) depends on the specific date and time passed, which can happen
- for political reasons. The default implementations of :meth:`astimezone` and
- :meth:`fromutc` may not produce the result you want if the result is one of the
- hours straddling the moment the standard offset changes.
- Skipping code for error cases, the default :meth:`fromutc` implementation acts
- like::
- def fromutc(self, dt):
- # raise ValueError error if dt.tzinfo is not self
- dtoff = dt.utcoffset()
- dtdst = dt.dst()
- # raise ValueError if dtoff is None or dtdst is None
- delta = dtoff - dtdst # this is self's standard offset
- if delta:
- dt += delta # convert to standard local time
- dtdst = dt.dst()
- # raise ValueError if dtdst is None
- if dtdst:
- return dt + dtdst
- else:
- return dt
- Example :class:`tzinfo` classes:
- .. literalinclude:: ../includes/tzinfo-examples.py
- Note that there are unavoidable subtleties twice per year in a :class:`tzinfo`
- subclass accounting for both standard and daylight time, at the DST transition
- points. For concreteness, consider US Eastern (UTC -0500), where EDT begins the
- minute after 1:59 (EST) on the first Sunday in April, and ends the minute after
- 1:59 (EDT) on the last Sunday in October::
- UTC 3:MM 4:MM 5:MM 6:MM 7:MM 8:MM
- EST 22:MM 23:MM 0:MM 1:MM 2:MM 3:MM
- EDT 23:MM 0:MM 1:MM 2:MM 3:MM 4:MM
- start 22:MM 23:MM 0:MM 1:MM 3:MM 4:MM
- end 23:MM 0:MM 1:MM 1:MM 2:MM 3:MM
- When DST starts (the "start" line), the local wall clock leaps from 1:59 to
- 3:00. A wall time of the form 2:MM doesn't really make sense on that day, so
- ``astimezone(Eastern)`` won't deliver a result with ``hour == 2`` on the day DST
- begins. In order for :meth:`astimezone` to make this guarantee, the
- :meth:`rzinfo.dst` method must consider times in the "missing hour" (2:MM for
- Eastern) to be in daylight time.
- When DST ends (the "end" line), there's a potentially worse problem: there's an
- hour that can't be spelled unambiguously in local wall time: the last hour of
- daylight time. In Eastern, that's times of the form 5:MM UTC on the day
- daylight time ends. The local wall clock leaps from 1:59 (daylight time) back
- to 1:00 (standard time) again. Local times of the form 1:MM are ambiguous.
- :meth:`astimezone` mimics the local clock's behavior by mapping two adjacent UTC
- hours into the same local hour then. In the Eastern example, UTC times of the
- form 5:MM and 6:MM both map to 1:MM when converted to Eastern. In order for
- :meth:`astimezone` to make this guarantee, the :meth:`tzinfo.dst` method must
- consider times in the "repeated hour" to be in standard time. This is easily
- arranged, as in the example, by expressing DST switch times in the time zone's
- standard local time.
- Applications that can't bear such ambiguities should avoid using hybrid
- :class:`tzinfo` subclasses; there are no ambiguities when using UTC, or any
- other fixed-offset :class:`tzinfo` subclass (such as a class representing only
- EST (fixed offset -5 hours), or only EDT (fixed offset -4 hours)).
- .. _strftime-behavior:
- :meth:`strftime` Behavior
- -------------------------
- :class:`date`, :class:`datetime`, and :class:`time` objects all support a
- ``strftime(format)`` method, to create a string representing the time under the
- control of an explicit format string. Broadly speaking, ``d.strftime(fmt)``
- acts like the :mod:`time` module's ``time.strftime(fmt, d.timetuple())``
- although not all objects support a :meth:`timetuple` method.
- For :class:`time` objects, the format codes for year, month, and day should not
- be used, as time objects have no such values. If they're used anyway, ``1900``
- is substituted for the year, and ``0`` for the month and day.
- For :class:`date` objects, the format codes for hours, minutes, seconds, and
- microseconds should not be used, as :class:`date` objects have no such
- values. If they're used anyway, ``0`` is substituted for them.
- .. versionadded:: 2.6
- :class:`time` and :class:`datetime` objects support a ``%f`` format code
- which expands to the number of microseconds in the object, zero-padded on
- the left to six places.
- For a naive object, the ``%z`` and ``%Z`` format codes are replaced by empty
- strings.
- For an aware object:
- ``%z``
- :meth:`utcoffset` is transformed into a 5-character string of the form +HHMM or
- -HHMM, where HH is a 2-digit string giving the number of UTC offset hours, and
- MM is a 2-digit string giving the number of UTC offset minutes. For example, if
- :meth:`utcoffset` returns ``timedelta(hours=-3, minutes=-30)``, ``%z`` is
- replaced with the string ``'-0330'``.
- ``%Z``
- If :meth:`tzname` returns ``None``, ``%Z`` is replaced by an empty string.
- Otherwise ``%Z`` is replaced by the returned value, which must be a string.
- The full set of format codes supported varies across platforms, because Python
- calls the platform C library's :func:`strftime` function, and platform
- variations are common.
- The following is a list of all the format codes that the C standard (1989
- version) requires, and these work on all platforms with a standard C
- implementation. Note that the 1999 version of the C standard added additional
- format codes.
- The exact range of years for which :meth:`strftime` works also varies across
- platforms. Regardless of platform, years before 1900 cannot be used.
- +-----------+--------------------------------+-------+
- | Directive | Meaning | Notes |
- +===========+================================+=======+
- | ``%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`` | Microsecond as a decimal | \(1) |
- | | number [0,999999], zero-padded | |
- | | on the left | |
- +-----------+--------------------------------+-------+
- | ``%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 | \(2) |
- | | AM or PM. | |
- +-----------+--------------------------------+-------+
- | ``%S`` | Second as a decimal number | \(3) |
- | | [00,61]. | |
- +-----------+--------------------------------+-------+
- | ``%U`` | Week number of the year | \(4) |
- | | (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. | |
- +-----------+--------------------------------+-------+
- | ``%w`` | Weekday as a decimal number | |
- | | [0(Sunday),6]. | |
- +-----------+--------------------------------+-------+
- | ``%W`` | Week number of the year | \(4) |
- | | (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. | |
- +-----------+--------------------------------+-------+
- | ``%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`` | UTC offset in the form +HHMM | \(5) |
- | | or -HHMM (empty string if the | |
- | | the object is naive). | |
- +-----------+--------------------------------+-------+
- | ``%Z`` | Time zone name (empty string | |
- | | if the object is naive). | |
- +-----------+--------------------------------+-------+
- | ``%%`` | A literal ``'%'`` character. | |
- +-----------+--------------------------------+-------+
- Notes:
- (1)
- When used with the :func:`strptime` function, the ``%f`` directive
- accepts from one to six digits and zero pads on the right. ``%f`` is
- an extension to the set of format characters in the C standard (but
- implemented separately in datetime objects, and therefore always
- available).
- (2)
- When used with the :func:`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``; according to the Posix standard this
- accounts for leap seconds and the (very rare) double leap seconds.
- The :mod:`time` module may produce and does accept leap seconds since
- it is based on the Posix standard, but the :mod:`datetime` module
- does not accept leap seconds in :func:`strptime` input nor will it
- produce them in :func:`strftime` output.
- (4)
- When used with the :func:`strptime` function, ``%U`` and ``%W`` are only used in
- calculations when the day of the week and the year are specified.
- (5)
- For example, if :meth:`utcoffset` returns ``timedelta(hours=-3, minutes=-30)``,
- ``%z`` is replaced with the string ``'-0330'``.