datetime
— 基本日期 时间类型
¶
源代码： Lib/datetime.py
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 attribute extraction for output formatting and manipulation. For related functionality, see also the
time
and
calendar
模块。
There are two kinds of date and time objects: “naive” and “aware”.
An aware object has sufficient knowledge of applicable algorithmic and political time adjustments, such as time zone and daylight saving time information, to locate itself relative to other aware objects. An aware object is used to represent a specific moment in time that is not open to interpretation [1] .
A naive object does not contain enough information to unambiguously locate itself relative to other date/time objects. Whether a naive object represents Coordinated Universal Time (UTC), local time, or time in some other timezone is purely up to the program, just like it is up to the program whether a particular number represents metres, miles, or mass. Naive objects are easy to understand and to work with, at the cost of ignoring some aspects of reality.
For applications requiring aware objects,
datetime
and
time
objects have an optional time zone information attribute,
tzinfo
, that can be set to an instance of a subclass of the abstract
tzinfo
class. These
tzinfo
objects capture information about the offset from UTC time, the time zone name, and whether Daylight Saving Time is in effect. Note that only one concrete
tzinfo
class, the
timezone
class, is supplied by the
datetime
模块。
timezone
class can represent simple timezones with fixed offset from UTC, such as UTC itself or North American EST and EDT timezones. Supporting timezones at deeper levels of detail is up to the application. The rules for time adjustment across the world are more political than rational, change frequently, and there is no standard suitable for every application aside from UTC.
datetime
模块导出下列常量：
datetime.
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:
hour
,
minute
,
second
,
microsecond
，和
tzinfo
.
datetime.
datetime
A combination of a date and a time. Attributes:
year
,
month
,
day
,
hour
,
minute
,
second
,
microsecond
，和
tzinfo
.
datetime.
timedelta
A duration expressing the difference between two
date
,
time
，或
datetime
instances to microsecond resolution.
datetime.
tzinfo
An abstract base class for time zone information objects. These are used by the
datetime
and
time
classes to provide a customizable notion of time adjustment (for example, to account for time zone and/or daylight saving time).
datetime.
timezone
A class that implements the
tzinfo
abstract base class as a fixed offset from the UTC.
3.2 版新增。
这些类型的对象是不可变的。
Objects of the
date
类型始终是单纯的。
An object of type
time
or
datetime
may be naive or aware. A
datetime
object
d
is aware if
d.tzinfo
不是
None
and
d.tzinfo.utcoffset(d)
does not return
None
。若
d.tzinfo
is
None
，或者若
d.tzinfo
不是
None
but
d.tzinfo.utcoffset(d)
返回
None
,
d
is naive. A
time
object
t
is aware if
t.tzinfo
不是
None
and
t.tzinfo.utcoffset(None)
does not return
None
。否则，
t
is naive.
The distinction between naive and aware doesn’t apply to
timedelta
对象。
子类关系：
object
timedelta
tzinfo
timezone
time
date
datetime
timedelta
对象
¶
A
timedelta
object represents a duration, the difference between two dates or times.
datetime.
timedelta
(
days=0
,
seconds=0
,
microseconds=0
,
milliseconds=0
,
minutes=0
,
hours=0
,
weeks=0
)
¶
所有自变量是可选的且默认为
0
. Arguments may be integers or floats, and may be positive or negative.
Only days , seconds and microseconds are stored internally. Arguments are converted to those units:
and days, seconds and microseconds are then normalized so that the representation is unique, with
0
<=
microseconds
<
1000000
0
<=
seconds
<
3600*24
(一天的秒数)
-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 using round-half-to-even tiebreaker. 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,
OverflowError
被引发。
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)
类属性：
timedelta.
max
¶
The most positive
timedelta
对象，
timedelta(days=999999999,
hours=23,
minutes=59,
seconds=59,
microseconds=999999)
.
timedelta.
resolution
¶
The smallest possible difference between non-equal
timedelta
objects,
timedelta(microseconds=1)
.
Note that, because of normalization,
timedelta.max
>
-timedelta.min
.
-timedelta.max
is not representable as a
timedelta
对象。
实例属性 (只读)：
| 属性 | Value |
|---|---|
days
|
Between -999999999 and 999999999 inclusive |
seconds
|
Between 0 and 86399 inclusive |
microseconds
|
Between 0 and 999999 inclusive |
支持的操作：
| 操作 | 结果 |
|---|---|
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)(6) |
t1
=
t2
*
i
or
t1
=
i
*
t2
|
Delta multiplied by an integer. Afterwards
t1
// i ==
t2
is true, provided
i
!=
0
.
|
| In general, t1 * i == t1 * (i-1) + t1 is true. (1) | |
t1
=
t2
*
f
or
t1
=
f
*
t2
|
Delta multiplied by a float. The result is rounded to the nearest multiple of timedelta.resolution using round-half-to-even. |
f
=
t2
/
t3
|
Division (3) of
t2
by
t3
. Returns a
float
对象。
|
t1
=
t2
/
f
or
t1
=
t2
/
i
|
Delta divided by a float or an int. The result is rounded to the nearest multiple of timedelta.resolution using round-half-to-even. |
t1
=
t2
//
i
or
t1
=
t2
//
t3
|
The floor is computed and the remainder (if any) is thrown away. In the second case, an integer is returned. (3) |
t1
=
t2
%
t3
|
The remainder is computed as a
timedelta
object. (3)
|
q,
r
=
divmod(t1,
t2)
|
Computes the quotient and the remainder:
q
=
t1
//
t2
(3) and
r
=
t1
%
t2
. q is an integer and r is a
timedelta
对象。
|
+t1
|
返回
timedelta
object with the same value. (2)
|
-t1
|
相当于
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)
|
str(t)
|
Returns a string in the form
[D
day[s],
][H]H:MM:SS[.UUUUUU]
, where D is negative for negative
t
. (5)
|
repr(t)
|
Returns a string in the form
datetime.timedelta(D[,
S[,
U]])
, where D is negative for negative
t
. (5)
|
注意事项：
This is exact, but may overflow.
This is exact, and cannot overflow.
Division by 0 raises
ZeroDivisionError
.
-
timedelta.max
is not representable as a
timedelta
对象。
String representations of
timedelta
objects are normalized similarly to their internal representation. This leads to somewhat unusual results for negative timedeltas. For example:
>>> timedelta(hours=-5)
datetime.timedelta(-1, 68400)
>>> print(_)
-1 day, 19:00:00
The expression
t2
-
t3
will always be equal to the expression
t2
+
(-t3)
except when t3 is equal to
timedelta.max
; in that case the former will produce a result while the latter will overflow.
In addition to the operations listed above
timedelta
objects support certain additions and subtractions with
date
and
datetime
objects (see below).
3.2 版改变：
Floor division and true division of a
timedelta
object by another
timedelta
object are now supported, as are remainder operations and the
divmod()
function. True division and multiplication of a
timedelta
object by a
float
object are now supported.
Comparisons of
timedelta
objects are supported with the
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
timedelta
object is compared to an object of a different type,
TypeError
is raised unless the comparison is
==
or
!=
. The latter cases return
False
or
True
，分别。
timedelta
对象是
hashable
(usable as dictionary keys), support efficient pickling, and in Boolean contexts, a
timedelta
object is considered to be true if and only if it isn’t equal to
timedelta(0)
.
实例方法：
timedelta.
total_seconds
(
)
¶
Return the total number of seconds contained in the duration. Equivalent to
td
/
timedelta(seconds=1)
.
Note that for very large time intervals (greater than 270 years on most platforms) this method will lose microsecond accuracy.
3.2 版新增。
用法范例：
>>> 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.total_seconds()
31536000.0
>>> 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
date
对象
¶
A
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.
datetime.
date
(
year
,
month
,
day
)
¶
All arguments are required. Arguments may be integers, in the following ranges:
MINYEAR
<=
year
<=
MAXYEAR
1
<=
month
<=
12
1
<=
day
<=
number
of
days
in
the
given
month
and
year
若给定自变量在那些范围之外，
ValueError
被引发。
其它构造函数，所有类方法：
date.
today
(
)
¶
Return the current local date. This is equivalent to
date.fromtimestamp(time.time())
.
date.
fromtimestamp
(
timestamp
)
¶
Return the local date corresponding to the POSIX timestamp, such as is returned by
time.time()
. This may raise
OverflowError
, if the timestamp is out of the range of values supported by the platform C
localtime()
function, and
OSError
on
localtime()
failure. 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
fromtimestamp()
.
3.3 版改变：
引发
OverflowError
而不是
ValueError
if the timestamp is out of the range of values supported by the platform C
localtime()
function. Raise
OSError
而不是
ValueError
on
localtime()
failure.
date.
fromordinal
(
ordinal
)
¶
Return the date corresponding to the proleptic Gregorian ordinal, where January 1 of year 1 has ordinal 1.
ValueError
is raised unless
1
<=
ordinal
<=
date.max.toordinal()
. For any date
d
,
date.fromordinal(d.toordinal())
==
d
.
类属性：
date.
min
¶
The earliest representable date,
date(MINYEAR,
1,
1)
.
date.
max
¶
The latest representable date,
date(MAXYEAR,
12,
31)
.
date.
resolution
¶
The smallest possible difference between non-equal date objects,
timedelta(days=1)
.
实例属性 (只读)：
date.
month
¶
在 1 至 12 (含 12) 之间。
date.
day
¶
Between 1 and the number of days in the given month of the given year.
支持的操作：
| 操作 | 结果 |
|---|---|
date2
=
date1
+
timedelta
|
date2
is
timedelta.days
days removed from
date1
. (1)
|
date2
=
date1
-
timedelta
|
Computes
date2
这样
date2
+
timedelta
==
date1
. (2)
|
timedelta
=
date1
-
date2
|
(3) |
date1
<
date2
|
date1 is considered less than date2 when date1 precedes date2 in time. (4) |
注意事项：
timedelta.days
>
0
, or backward if
timedelta.days
<
0
. Afterward
date2
-
date1
==
timedelta.days
.
timedelta.seconds
and
timedelta.microseconds
被忽略。
OverflowError
is raised if
date2.year
would be smaller than
MINYEAR
or larger than
MAXYEAR
.
timedelta.seconds
and
timedelta.microseconds
被忽略。
date1
<
date2
if and only if
date1.toordinal()
<
date2.toordinal()
. Date comparison raises
TypeError
if
the other comparand isn’t also a
date
object. However,
NotImplemented
is returned instead if the other comparand has a
timetuple()
attribute. This hook gives other kinds of date objects a
chance at implementing mixed-type comparison. If not, when a
date
object is compared to an object of a different type,
TypeError
is raised
unless the comparison is
==
or
!=
. The latter cases return
False
or
True
，分别。
Dates can be used as dictionary keys. In Boolean contexts, all
date
objects are considered to be true.
实例方法：
date.
replace
(
year=self.year
,
month=self.month
,
day=self.day
)
¶
Return a date with the same value, except for those parameters 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)
.
date.
timetuple
(
)
¶
返回
time.struct_time
such as returned by
time.localtime()
. The hours, minutes and seconds are 0, and the DST flag is -1.
d.timetuple()
相当于
time.struct_time((d.year,
d.month,
d.day,
0,
0,
0,
d.weekday(),
yday,
-1))
，其中
yday
=
d.toordinal()
-
date(d.year,
1,
1).toordinal()
+
1
is the day number within the current year starting with
1
for January 1st.
date.
toordinal
(
)
¶
Return the proleptic Gregorian ordinal of the date, where January 1 of year 1 has ordinal 1. For any
date
object
d
,
date.fromordinal(d.toordinal())
==
d
.
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
isoweekday()
.
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
weekday()
,
isocalendar()
.
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 https://www.staff.science.uu.nl/~gent0113/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)
.
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__
(
)
¶
For a date
d
,
str(d)
相当于
d.isoformat()
.
date.
ctime
(
)
¶
Return a string representing the date, for example
date(2002,
12,
4).ctime()
==
'Wed
Dec
4
00:00:00
2002'
.
d.ctime()
相当于
time.ctime(time.mktime(d.timetuple()))
on platforms where the native C
ctime()
function (which
time.ctime()
invokes, but which
date.ctime()
does not invoke) conforms to the C standard.
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. For a complete list of formatting directives, see strftime() 和 strptime() 行为 .
date.
__format__
(
format
)
¶
如同
date.strftime()
. This makes it possible to specify a format string for a
date
object in
格式化字符串文字
and when using
str.format()
. For a complete list of formatting directives, see
strftime() 和 strptime() 行为
.
计算事件天数的范例：
>>> 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
date
:
>>> 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.'
datetime
对象
¶
A
datetime
object is a single object containing all the information from a
date
object and a
time
object. Like a
date
对象，
datetime
assumes the current Gregorian calendar extended in both directions; like a time object,
datetime
assumes there are exactly 3600*24 seconds in every day.
构造函数：
datetime.
datetime
(
year
,
month
,
day
,
hour=0
,
minute=0
,
second=0
,
microsecond=0
,
tzinfo=None
,
*
,
fold=0
)
¶
The year, month and day arguments are required.
tzinfo
可以是
None
, or an instance of a
tzinfo
subclass. The remaining arguments may be integers, 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
,
fold
in
[0,
1]
.
若给定自变量在那些范围之外，
ValueError
被引发。
3.6 版新增：
添加
fold
自变量。
其它构造函数，所有类方法：
datetime.
today
(
)
¶
Return the current local datetime, with
tzinfo
None
。这相当于
datetime.fromtimestamp(time.time())
。另请参阅
now()
,
fromtimestamp()
.
datetime.
now
(
tz=None
)
¶
Return the current local date and time. If optional argument
tz
is
None
or not specified, this is like
today()
, but, if possible, supplies more precision than can be gotten from going through a
time.time()
timestamp (for example, this may be possible on platforms supplying the C
gettimeofday()
function).
若
tz
不是
None
, it must be an instance of a
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))
。另请参阅
today()
,
utcnow()
.
datetime.
utcnow
(
)
¶
Return the current UTC date and time, with
tzinfo
None
. This is like
now()
, but returns the current UTC date and time, as a naive
datetime
object. An aware current UTC datetime can be obtained by calling
datetime.now(timezone.utc)
。另请参阅
now()
.
datetime.
fromtimestamp
(
timestamp
,
tz=None
)
¶
Return the local date and time corresponding to the POSIX timestamp, such as is returned by
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
datetime
object is naive.
若
tz
不是
None
, it must be an instance of a
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))
.
fromtimestamp()
may raise
OverflowError
, if the timestamp is out of the range of values supported by the platform C
localtime()
or
gmtime()
functions, and
OSError
on
localtime()
or
gmtime()
failure. 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
fromtimestamp()
, and then it’s possible to have two timestamps differing by a second that yield identical
datetime
objects. See also
utcfromtimestamp()
.
3.3 版改变：
引发
OverflowError
而不是
ValueError
if the timestamp is out of the range of values supported by the platform C
localtime()
or
gmtime()
functions. Raise
OSError
而不是
ValueError
on
localtime()
or
gmtime()
failure.
3.6 版改变：
fromtimestamp()
may return instances with
fold
set to 1.
datetime.
utcfromtimestamp
(
timestamp
)
¶
Return the UTC
datetime
corresponding to the POSIX timestamp, with
tzinfo
None
. This may raise
OverflowError
, if the timestamp is out of the range of values supported by the platform C
gmtime()
function, and
OSError
on
gmtime()
failure. It’s common for this to be restricted to years in 1970 through 2038.
To get an aware
datetime
object, call
fromtimestamp()
:
datetime.fromtimestamp(timestamp, timezone.utc)
On the POSIX compliant platforms, it is equivalent to the following expression:
datetime(1970, 1, 1, tzinfo=timezone.utc) + timedelta(seconds=timestamp)
except the latter formula always supports the full years range: between
MINYEAR
and
MAXYEAR
包含在内。
3.3 版改变：
引发
OverflowError
而不是
ValueError
if the timestamp is out of the range of values supported by the platform C
gmtime()
function. Raise
OSError
而不是
ValueError
on
gmtime()
failure.
datetime.
fromordinal
(
ordinal
)
¶
返回
datetime
corresponding to the proleptic Gregorian ordinal, where January 1 of year 1 has ordinal 1.
ValueError
is raised unless
1
<=
ordinal
<=
datetime.max.toordinal()
. The hour, minute, second and microsecond of the result are all 0, and
tzinfo
is
None
.
datetime.
combine
(
date
,
time
,
tzinfo=self.tzinfo
)
¶
返回新
datetime
object whose date components are equal to the given
date
object’s, and whose time components are equal to the given
time
object’s. If the
tzinfo
argument is provided, its value is used to set the
tzinfo
attribute of the result, otherwise the
tzinfo
属性在
time
argument is used.
For any
datetime
object
d
,
d
==
datetime.combine(d.date(),
d.time(),
d.tzinfo)
. If date is a
datetime
object, its time components and
tzinfo
attributes are ignored.
3.6 版改变： 添加 tzinfo 自变量。
datetime.
strptime
(
date_string
,
format
)
¶
返回
datetime
corresponding to
date_string
, parsed according to
format
。这相当于
datetime(*(time.strptime(date_string,
format)[0:6]))
.
ValueError
is raised if the date_string and format can’t be parsed by
time.strptime()
or if it returns a value which isn’t a time tuple. For a complete list of formatting directives, see
strftime() 和 strptime() 行为
.
类属性：
datetime.
max
¶
The latest representable
datetime
,
datetime(MAXYEAR,
12,
31,
23,
59,
59,
999999,
tzinfo=None)
.
datetime.
resolution
¶
The smallest possible difference between non-equal
datetime
objects,
timedelta(microseconds=1)
.
实例属性 (只读)：
datetime.
month
¶
在 1 至 12 (含 12) 之间。
datetime.
day
¶
Between 1 and the number of days in the given month of the given year.
datetime.
hour
¶
在
range(24)
.
datetime.
minute
¶
在
range(60)
.
datetime.
second
¶
在
range(60)
.
datetime.
microsecond
¶
在
range(1000000)
.
datetime.
tzinfo
¶
The object passed as the
tzinfo
argument to the
datetime
constructor, or
None
if none was passed.
datetime.
fold
¶
在
[0,
1]
. Used to disambiguate wall times during a repeated interval. (A repeated interval occurs when clocks are rolled back at the end of daylight saving time or when the UTC offset for the current zone is decreased for political reasons.) The value 0 (1) represents the earlier (later) of the two moments with the same wall time representation.
3.6 版新增。
支持的操作：
| 操作 | 结果 |
|---|---|
datetime2
=
datetime1
+
timedelta
|
(1) |
datetime2
=
datetime1
-
timedelta
|
(2) |
timedelta
=
datetime1
-
datetime2
|
(3) |
datetime1
<
datetime2
|
比较
datetime
to
datetime
. (4)
|
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
tzinfo
attribute as the input datetime, and datetime2 - datetime1 == timedelta after.
OverflowError
is raised if datetime2.year would be smaller than
MINYEAR
or larger than
MAXYEAR
. Note that no time zone adjustments are done even if the input is an aware object.
Computes the datetime2 such that datetime2 + timedelta == datetime1. As for addition, the result has the same
tzinfo
attribute as the input datetime, and no time zone adjustments are done even if the input is aware.
Subtraction of a
datetime
from a
datetime
is defined only if both operands are naive, or if both are aware. If one is aware and the other is naive,
TypeError
被引发。
If both are naive, or both are aware and have the same
tzinfo
attribute, the
tzinfo
attributes are ignored, and the result is a
timedelta
object
t
这样
datetime2
+
t
==
datetime1
. No time zone adjustments are done in this case.
If both are aware and have different
tzinfo
attributes,
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.
datetime1 is considered less than datetime2 when datetime1 precedes datetime2 in time.
If one comparand is naive and the other is aware,
TypeError
is raised if an order comparison is attempted. For equality comparisons, naive instances are never equal to aware instances.
If both comparands are aware, and have the same
tzinfo
attribute, the common
tzinfo
attribute is ignored and the base datetimes are compared. If both comparands are aware and have different
tzinfo
attributes, the comparands are first adjusted by subtracting their UTC offsets (obtained from
self.utcoffset()
).
注意
In order to stop comparison from falling back to the default scheme of comparing object addresses, datetime comparison normally raises
TypeError
if the other comparand isn’t also a
datetime
object. However,
NotImplemented
is returned instead if the other comparand has a
timetuple()
attribute. This hook gives other kinds of date objects a chance at implementing mixed-type comparison. If not, when a
datetime
object is compared to an object of a different type,
TypeError
is raised unless the comparison is
==
or
!=
. The latter cases return
False
or
True
，分别。
datetime
objects can be used as dictionary keys. In Boolean contexts, all
datetime
objects are considered to be true.
实例方法：
datetime.
time
(
)
¶
返回
time
object with same hour, minute, second, microsecond and fold.
tzinfo
is
None
. See also method
timetz()
.
3.6 版改变：
The fold value is copied to the returned
time
对象。
datetime.
timetz
(
)
¶
返回
time
object with same hour, minute, second, microsecond, fold, and tzinfo attributes. See also method
time()
.
3.6 版改变：
The fold value is copied to the returned
time
对象。
datetime.
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
)
¶
Return a datetime with the same attributes, except for those attributes 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 data.
3.6 版新增：
添加
fold
自变量。
datetime.
astimezone
(
tz=None
)
¶
返回
datetime
object with new
tzinfo
属性
tz
, adjusting the date and time data so the result is the same UTC time as
self
, but in
tz
’s local time.
If provided,
tz
must be an instance of a
tzinfo
subclass, and its
utcoffset()
and
dst()
methods must not return
None
。若
self
is naive, it is presumed to represent time in the system timezone.
If called without arguments (or with
tz=None
) the system local timezone is assumed for the target timezone. The
.tzinfo
attribute of the converted datetime instance will be set to an instance of
timezone
with the zone name and offset obtained from the OS.
若
self.tzinfo
is
tz
,
self.astimezone(tz)
等于
self
: no adjustment of date or time data is performed. Else the result is local time in the timezone
tz
, representing the same UTC time as
self
: after
astz
=
dt.astimezone(tz)
,
astz
-
astz.utcoffset()
will have the same date and time data as
dt
-
dt.utcoffset()
.
If you merely want to attach a time zone object
tz
to a datetime
dt
without adjustment of date and time data, 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 data, use
dt.replace(tzinfo=None)
.
Note that the default
tzinfo.fromutc()
method can be overridden in a
tzinfo
subclass to affect the result returned by
astimezone()
. Ignoring error cases,
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)
3.3 版改变： tz now can be omitted.
3.6 版改变：
astimezone()
method can now be called on naive instances that are presumed to represent system local time.
datetime.
utcoffset
(
)
¶
若
tzinfo
is
None
, returns
None
, else returns
self.tzinfo.utcoffset(self)
, and raises an exception if the latter doesn’t return
None
，或
timedelta
object representing a whole number of minutes with magnitude less than one day.
datetime.
dst
(
)
¶
若
tzinfo
is
None
, returns
None
, else returns
self.tzinfo.dst(self)
, and raises an exception if the latter doesn’t return
None
，或
timedelta
object representing a whole number of minutes with magnitude less than one day.
datetime.
tzname
(
)
¶
若
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,
datetime.
timetuple
(
)
¶
返回
time.struct_time
such as returned by
time.localtime()
.
d.timetuple()
相当于
time.struct_time((d.year,
d.month,
d.day,
d.hour,
d.minute,
d.second,
d.weekday(),
yday,
dst))
，其中
yday
=
d.toordinal()
-
date(d.year,
1,
1).toordinal()
+
1
is the day number within the current year starting with
1
for January 1st. The
tm_isdst
flag of the result is set according to the
dst()
方法：
tzinfo
is
None
or
dst()
返回
None
,
tm_isdst
被设为
-1
; else if
dst()
returns a non-zero value,
tm_isdst
被设为
1
; else
tm_isdst
被设为
0
.
datetime.
utctimetuple
(
)
¶
若
datetime
instance
d
is naive, this is the same as
d.timetuple()
except that
tm_isdst
is forced to 0 regardless of what
d.dst()
returns. DST is never in effect for a UTC time.
若
d
is aware,
d
is normalized to UTC time, by subtracting
d.utcoffset()
，和
time.struct_time
for the normalized time is returned.
tm_isdst
is forced to 0. Note that an
OverflowError
may be raised if
d
.year was
MINYEAR
or
MAXYEAR
and UTC adjustment spills over a year boundary.
datetime.
toordinal
(
)
¶
Return the proleptic Gregorian ordinal of the date. The same as
self.date().toordinal()
.
datetime.
timestamp
(
)
¶
Return POSIX timestamp corresponding to the
datetime
instance. The return value is a
float
similar to that returned by
time.time()
.
Naive
datetime
instances are assumed to represent local time and this method relies on the platform C
mktime()
function to perform the conversion. Since
datetime
supports wider range of values than
mktime()
on many platforms, this method may raise
OverflowError
for times far in the past or far in the future.
For aware
datetime
instances, the return value is computed as:
(dt - datetime(1970, 1, 1, tzinfo=timezone.utc)).total_seconds()
3.3 版新增。
3.6 版改变：
timestamp()
method uses the
fold
attribute to disambiguate the times during a repeated interval.
注意
There is no method to obtain the POSIX timestamp directly from a naive
datetime
instance representing UTC time. If your application uses this convention and your system timezone is not set to UTC, you can obtain the POSIX timestamp by supplying
tzinfo=timezone.utc
:
timestamp = dt.replace(tzinfo=timezone.utc).timestamp()
or by calculating the timestamp directly:
timestamp = (dt - datetime(1970, 1, 1)) / timedelta(seconds=1)
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()
。另请参阅
isoweekday()
.
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()
。另请参阅
weekday()
,
isocalendar()
.
datetime.
isocalendar
(
)
¶
Return a 3-tuple, (ISO year, ISO week number, ISO weekday). The same as
self.date().isocalendar()
.
datetime.
isoformat
(
sep='T'
,
timespec='auto'
)
¶
Return a string representing the date and time in ISO 8601 format, YYYY-MM-DDTHH:MM:SS.mmmmmm or, if
microsecond
is 0, YYYY-MM-DDTHH:MM:SS
若
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
microsecond
is 0 YYYY-MM-DDTHH:MM:SS+HH:MM
可选自变量
sep
(默认
'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'
可选自变量
timespec
specifies the number of additional components of the time to include (the default is
'auto'
). It can be one of the following:
'auto'
: Same as
'seconds'
if
microsecond
is 0, same as
'microseconds'
否则。
'hours'
: Include the
hour
in the two-digit HH format.
'minutes'
: Include
hour
and
minute
in HH:MM format.
'seconds'
: Include
hour
,
minute
，和
second
in HH:MM:SS format.
'milliseconds'
: Include full time, but truncate fractional second part to milliseconds. HH:MM:SS.sss format.
'microseconds'
: Include full time in HH:MM:SS.mmmmmm format.
注意
Excluded time components are truncated, not rounded.
ValueError
will be raised on an invalid
timespec
自变量。
>>> from datetime import datetime
>>> datetime.now().isoformat(timespec='minutes')
'2002-12-25T00:00'
>>> dt = datetime(2015, 1, 1, 12, 30, 59, 0)
>>> dt.isoformat(timespec='microseconds')
'2015-01-01T12:30:59.000000'
3.6 版新增： 添加 timespec 自变量。
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()
相当于
time.ctime(time.mktime(d.timetuple()))
on platforms where the native C
ctime()
function (which
time.ctime()
invokes, but which
datetime.ctime()
does not invoke) conforms to the C standard.
datetime.
strftime
(
format
)
¶
Return a string representing the date and time, controlled by an explicit format string. For a complete list of formatting directives, see strftime() 和 strptime() 行为 .
datetime.
__format__
(
format
)
¶
如同
datetime.strftime()
. This makes it possible to specify a format string for a
datetime
object in
格式化字符串文字
and when using
str.format()
. For a complete list of formatting directives, see
strftime() 和 strptime() 行为
.
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 # 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
time
对象
¶
A time object represents a (local) time of day, independent of any particular day, and subject to adjustment via a
tzinfo
对象。
datetime.
time
(
hour=0
,
minute=0
,
second=0
,
microsecond=0
,
tzinfo=None
,
*
,
fold=0
)
¶
All arguments are optional.
tzinfo
可以是
None
, or an instance of a
tzinfo
subclass. The remaining arguments may be integers, in the following ranges:
0
<=
hour
<
24
,
0
<=
minute
<
60
,
0
<=
second
<
60
,
0
<=
microsecond
<
1000000
,
fold
in
[0,
1]
.
若给定自变量在那些范围之外，
ValueError
is raised. All default to
0
except
tzinfo
，其默认为
None
.
类属性：
time.
resolution
¶
The smallest possible difference between non-equal
time
objects,
timedelta(microseconds=1)
, although note that arithmetic on
time
objects is not supported.
实例属性 (只读)：
time.
hour
¶
在
range(24)
.
time.
minute
¶
在
range(60)
.
time.
second
¶
在
range(60)
.
time.
microsecond
¶
在
range(1000000)
.
time.
tzinfo
¶
The object passed as the tzinfo argument to the
time
constructor, or
None
if none was passed.
time.
fold
¶
在
[0,
1]
. Used to disambiguate wall times during a repeated interval. (A repeated interval occurs when clocks are rolled back at the end of daylight saving time or when the UTC offset for the current zone is decreased for political reasons.) The value 0 (1) represents the earlier (later) of the two moments with the same wall time representation.
3.6 版新增。
支持的操作：
comparison of
time
to
time
，其中
a
is considered less than
b
when
a
precedes
b
in time. If one comparand is naive and the other is aware,
TypeError
is raised if an order comparison is attempted. For equality comparisons, naive instances are never equal to aware instances.
If both comparands are aware, and have the same
tzinfo
attribute, the common
tzinfo
attribute is ignored and the base times are compared. If both comparands are aware and have different
tzinfo
attributes, 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
time
object is compared to an object of a different type,
TypeError
is raised unless the comparison is
==
or
!=
. The latter cases return
False
or
True
，分别。
hash, use as dict key
efficient pickling
In boolean contexts, a
time
object is always considered to be true.
3.5 版改变：
Before Python 3.5, a
time
object was considered to be false if it represented midnight in UTC. This behavior was considered obscure and error-prone and has been removed in Python 3.5. See
bpo-13936
for full details.
实例方法：
time.
replace
(
hour=self.hour
,
minute=self.minute
,
second=self.second
,
microsecond=self.microsecond
,
tzinfo=self.tzinfo
,
* fold=0
)
¶
返回
time
with the same value, except for those attributes given new values by whichever keyword arguments are specified. Note that
tzinfo=None
can be specified to create a naive
time
from an aware
time
, without conversion of the time data.
3.6 版新增：
添加
fold
自变量。
time.
isoformat
(
timespec='auto'
)
¶
Return a string representing the time in ISO 8601 format, HH:MM:SS.mmmmmm or, if
microsecond
is 0, HH:MM:SS If
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
可选自变量
timespec
specifies the number of additional components of the time to include (the default is
'auto'
). It can be one of the following:
'auto'
: Same as
'seconds'
if
microsecond
is 0, same as
'microseconds'
否则。
'hours'
: Include the
hour
in the two-digit HH format.
'minutes'
: Include
hour
and
minute
in HH:MM format.
'seconds'
: Include
hour
,
minute
，和
second
in HH:MM:SS format.
'milliseconds'
: Include full time, but truncate fractional second part to milliseconds. HH:MM:SS.sss format.
'microseconds'
: Include full time in HH:MM:SS.mmmmmm format.
注意
Excluded time components are truncated, not rounded.
ValueError
will be raised on an invalid
timespec
自变量。
>>> from datetime import time
>>> time(hour=12, minute=34, second=56, microsecond=123456).isoformat(timespec='minutes')
'12:34'
>>> dt = time(hour=12, minute=34, second=56, microsecond=0)
>>> dt.isoformat(timespec='microseconds')
'12:34:56.000000'
>>> dt.isoformat(timespec='auto')
'12:34:56'
3.6 版新增： 添加 timespec 自变量。
time.
__str__
(
)
¶
For a time
t
,
str(t)
相当于
t.isoformat()
.
time.
strftime
(
format
)
¶
Return a string representing the time, controlled by an explicit format string. For a complete list of formatting directives, see strftime() 和 strptime() 行为 .
time.
__format__
(
format
)
¶
如同
time.strftime()
. This makes it possible to specify a format string for a
time
object in
格式化字符串文字
and when using
str.format()
. For a complete list of formatting directives, see
strftime() 和 strptime() 行为
.
time.
utcoffset
(
)
¶
若
tzinfo
is
None
, returns
None
, else returns
self.tzinfo.utcoffset(None)
, and raises an exception if the latter doesn’t return
None
或
timedelta
object representing a whole number of minutes with magnitude less than one day.
time.
dst
(
)
¶
若
tzinfo
is
None
, returns
None
, else returns
self.tzinfo.dst(None)
, and raises an exception if the latter doesn’t return
None
，或
timedelta
object representing a whole number of minutes with magnitude less than one day.
time.
tzname
(
)
¶
若
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.
范例：
>>> from datetime import time, tzinfo, timedelta
>>> 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'
>>> 'The {} is {:%H:%M}.'.format("time", t)
'The time is 12:10.'
tzinfo
对象
¶
datetime.
tzinfo
¶
This 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
tzinfo
methods needed by the
datetime
methods you use. The
datetime
module supplies a simple concrete subclass of
tzinfo
,
timezone
, which can represent timezones with fixed offset from UTC such as UTC itself or North American EST and EDT.
An instance of (a concrete subclass of)
tzinfo
can be passed to the constructors for
datetime
and
time
objects. The latter objects view their attributes as being in local time, and the
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
tzinfo
subclass must have an
__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
tzinfo
may need to implement the following methods. Exactly which methods are needed depends on the uses made of aware
datetime
objects. If in doubt, simply implement all of them.
tzinfo.
utcoffset
(
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
tzinfo
object represents both time zone and DST adjustments,
utcoffset()
should return their sum. If the UTC offset isn’t known, return
None
. Else the value returned must be a
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
utcoffset()
will probably look like one of these two:
return CONSTANT # fixed-offset class
return CONSTANT + self.dst(dt) # daylight-aware class
若
utcoffset()
does not return
None
,
dst()
should not return
None
either.
The default implementation of
utcoffset()
引发
NotImplementedError
.
tzinfo.
dst
(
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
timedelta
object (see
utcoffset()
for details). Note that DST offset, if applicable, has already been added to the UTC offset returned by
utcoffset()
, so there’s no need to consult
dst()
unless you’re interested in obtaining DST info separately. For example,
datetime.timetuple()
calls its
tzinfo
attribute’s
dst()
method to determine how the
tm_isdst
flag should be set, and
tzinfo.fromutc()
calls
dst()
to account for DST changes when crossing time zones.
An instance
tz
of a
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
datetime
dt
with
dt.tzinfo
==
tz
For sane
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
datetime.astimezone()
relies on this, but cannot detect violations; it’s the programmer’s responsibility to ensure it. If a
tzinfo
subclass cannot guarantee this, it may be able to override the default implementation of
tzinfo.fromutc()
to work correctly with
astimezone()
regardless.
Most implementations of
dst()
will probably look like one of these two:
def dst(self, dt):
# a fixed-offset class: doesn't account for DST
return timedelta(0)
or
def dst(self, dt):
# 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
dst()
引发
NotImplementedError
.
tzinfo.
tzname
(
dt
)
¶
Return the time zone name corresponding to the
datetime
object
dt
, as a string. Nothing about string names is defined by the
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
tzinfo
subclasses will wish to return different names depending on the specific value of
dt
passed, especially if the
tzinfo
class is accounting for daylight time.
The default implementation of
tzname()
引发
NotImplementedError
.
These methods are called by a
datetime
or
time
object, in response to their methods of the same names. A
datetime
object passes itself as the argument, and a
time
object passes
None
as the argument. A
tzinfo
subclass’s methods should therefore be prepared to accept a
dt
argument of
None
, or of class
datetime
.
当
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
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.
当
datetime
object is passed in response to a
datetime
method,
dt.tzinfo
is the same object as
self
.
tzinfo
methods can rely on this, unless user code calls
tzinfo
methods directly. The intent is that the
tzinfo
methods interpret
dt
as being in local time, and not need worry about objects in other timezones.
There is one more
tzinfo
method that a subclass may wish to override:
tzinfo.
fromutc
(
dt
)
¶
This is called from the default
datetime.astimezone()
implementation. When called from that,
dt.tzinfo
is
self
，和
dt
’s date and time data are to be viewed as expressing a UTC time. The purpose of
fromutc()
is to adjust the date and time data, returning an equivalent datetime in
self
’s local time.
Most
tzinfo
subclasses should be able to inherit the default
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
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
astimezone()
and
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
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
范例
tzinfo
类：
from datetime import tzinfo, timedelta, datetime, timezone
ZERO = timedelta(0)
HOUR = timedelta(hours=1)
SECOND = timedelta(seconds=1)
# A class capturing the platform's idea of local time.
# (May result in wrong values on historical times in
# timezones where UTC offset and/or the DST rules had
# changed in the past.)
import time as _time
STDOFFSET = timedelta(seconds = -_time.timezone)
if _time.daylight:
DSTOFFSET = timedelta(seconds = -_time.altzone)
else:
DSTOFFSET = STDOFFSET
DSTDIFF = DSTOFFSET - STDOFFSET
class LocalTimezone(tzinfo):
def fromutc(self, dt):
assert dt.tzinfo is self
stamp = (dt - datetime(1970, 1, 1, tzinfo=self)) // SECOND
args = _time.localtime(stamp)[:6]
dst_diff = DSTDIFF // SECOND
# Detect fold
fold = (args == _time.localtime(stamp - dst_diff))
return datetime(*args, microsecond=dt.microsecond,
tzinfo=self, fold=fold)
def utcoffset(self, dt):
if self._isdst(dt):
return DSTOFFSET
else:
return STDOFFSET
def dst(self, dt):
if self._isdst(dt):
return DSTDIFF
else:
return ZERO
def tzname(self, dt):
return _time.tzname[self._isdst(dt)]
def _isdst(self, dt):
tt = (dt.year, dt.month, dt.day,
dt.hour, dt.minute, dt.second,
dt.weekday(), 0, 0)
stamp = _time.mktime(tt)
tt = _time.localtime(stamp)
return tt.tm_isdst > 0
Local = LocalTimezone()
# A complete implementation of current DST rules for major US time zones.
def first_sunday_on_or_after(dt):
days_to_go = 6 - dt.weekday()
if days_to_go:
dt += timedelta(days_to_go)
return dt
# US DST Rules
#
# This is a simplified (i.e., wrong for a few cases) set of rules for US
# DST start and end times. For a complete and up-to-date set of DST rules
# and timezone definitions, visit the Olson Database (or try pytz):
# http://www.twinsun.com/tz/tz-link.htm
# http://sourceforge.net/projects/pytz/ (might not be up-to-date)
#
# In the US, since 2007, DST starts at 2am (standard time) on the second
# Sunday in March, which is the first Sunday on or after Mar 8.
DSTSTART_2007 = datetime(1, 3, 8, 2)
# and ends at 2am (DST time) on the first Sunday of Nov.
DSTEND_2007 = datetime(1, 11, 1, 2)
# From 1987 to 2006, DST used to start at 2am (standard time) on the first
# Sunday in April and to end at 2am (DST time) on the last
# Sunday of October, which is the first Sunday on or after Oct 25.
DSTSTART_1987_2006 = datetime(1, 4, 1, 2)
DSTEND_1987_2006 = datetime(1, 10, 25, 2)
# From 1967 to 1986, DST used to start at 2am (standard time) on the last
# Sunday in April (the one on or after April 24) and to end at 2am (DST time)
# on the last Sunday of October, which is the first Sunday
# on or after Oct 25.
DSTSTART_1967_1986 = datetime(1, 4, 24, 2)
DSTEND_1967_1986 = DSTEND_1987_2006
def us_dst_range(year):
# Find start and end times for US DST. For years before 1967, return
# start = end for no DST.
if 2006 < year:
dststart, dstend = DSTSTART_2007, DSTEND_2007
elif 1986 < year < 2007:
dststart, dstend = DSTSTART_1987_2006, DSTEND_1987_2006
elif 1966 < year < 1987:
dststart, dstend = DSTSTART_1967_1986, DSTEND_1967_1986
else:
return (datetime(year, 1, 1), ) * 2
start = first_sunday_on_or_after(dststart.replace(year=year))
end = first_sunday_on_or_after(dstend.replace(year=year))
return start, end
class USTimeZone(tzinfo):
def __init__(self, hours, reprname, stdname, dstname):
self.stdoffset = timedelta(hours=hours)
self.reprname = reprname
self.stdname = stdname
self.dstname = dstname
def __repr__(self):
return self.reprname
def tzname(self, dt):
if self.dst(dt):
return self.dstname
else:
return self.stdname
def utcoffset(self, dt):
return self.stdoffset + self.dst(dt)
def dst(self, dt):
if dt is None or dt.tzinfo is None:
# An exception may be sensible here, in one or both cases.
# It depends on how you want to treat them. The default
# fromutc() implementation (called by the default astimezone()
# implementation) passes a datetime with dt.tzinfo is self.
return ZERO
assert dt.tzinfo is self
start, end = us_dst_range(dt.year)
# Can't compare naive to aware objects, so strip the timezone from
# dt first.
dt = dt.replace(tzinfo=None)
if start + HOUR <= dt < end - HOUR:
# DST is in effect.
return HOUR
if end - HOUR <= dt < end:
# Fold (an ambiguous hour): use dt.fold to disambiguate.
return ZERO if dt.fold else HOUR
if start <= dt < start + HOUR:
# Gap (a non-existent hour): reverse the fold rule.
return HOUR if dt.fold else ZERO
# DST is off.
return ZERO
def fromutc(self, dt):
assert dt.tzinfo is self
start, end = us_dst_range(dt.year)
start = start.replace(tzinfo=self)
end = end.replace(tzinfo=self)
std_time = dt + self.stdoffset
dst_time = std_time + HOUR
if end <= dst_time < end + HOUR:
# Repeated hour
return std_time.replace(fold=1)
if std_time < start or dst_time >= end:
# Standard time
return std_time
if start <= std_time < end - HOUR:
# Daylight saving time
return dst_time
Eastern = USTimeZone(-5, "Eastern", "EST", "EDT")
Central = USTimeZone(-6, "Central", "CST", "CDT")
Mountain = USTimeZone(-7, "Mountain", "MST", "MDT")
Pacific = USTimeZone(-8, "Pacific", "PST", "PDT")
Note that there are unavoidable subtleties twice per year in a
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 second Sunday in March, and ends the minute after 1:59 (EDT) on the first Sunday in November:
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. For example, at the Spring forward transition of 2016, we get
>>> u0 = datetime(2016, 3, 13, 5, tzinfo=timezone.utc)
>>> for i in range(4):
... u = u0 + i*HOUR
... t = u.astimezone(Eastern)
... print(u.time(), 'UTC =', t.time(), t.tzname())
...
05:00:00 UTC = 00:00:00 EST
06:00:00 UTC = 01:00:00 EST
07:00:00 UTC = 03:00:00 EDT
08:00:00 UTC = 04:00:00 EDT
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.
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, but earlier times have the
fold
attribute set to 0 and the later times have it set to 1. For example, at the Fall back transition of 2016, we get
>>> u0 = datetime(2016, 11, 6, 4, tzinfo=timezone.utc)
>>> for i in range(4):
... u = u0 + i*HOUR
... t = u.astimezone(Eastern)
... print(u.time(), 'UTC =', t.time(), t.tzname(), t.fold)
...
04:00:00 UTC = 00:00:00 EDT 0
05:00:00 UTC = 01:00:00 EDT 0
06:00:00 UTC = 01:00:00 EST 1
07:00:00 UTC = 02:00:00 EST 0
注意，
datetime
instances that differ only by the value of the
fold
attribute are considered equal in comparisons.
Applications that can’t bear wall-time ambiguities should explicitly check the value of the
fold
attribute or avoid using hybrid
tzinfo
subclasses; there are no ambiguities when using
timezone
, or any other fixed-offset
tzinfo
subclass (such as a class representing only EST (fixed offset -5 hours), or only EDT (fixed offset -4 hours)).
另请参阅
The standard library has
timezone
class for handling arbitrary fixed offsets from UTC and
timezone.utc
as UTC timezone instance.
dateutil.tz library brings the IANA timezone database (also known as the Olson database) to Python and its usage is recommended.
timezone
对象
¶
timezone
类是子类化的
tzinfo
, each instance of which represents a timezone defined by a fixed offset from UTC. Note that objects of this class cannot be used to represent timezone information in the locations where different offsets are used in different days of the year or where historical changes have been made to civil time.
datetime.
timezone
(
offset
,
name=None
)
¶
offset
argument must be specified as a
timedelta
object representing the difference between the local time and UTC. It must be strictly between
-timedelta(hours=24)
and
timedelta(hours=24)
and represent a whole number of minutes, otherwise
ValueError
被引发。
name
argument is optional. If specified it must be a string that will be used as the value returned by the
datetime.tzname()
方法。
3.2 版新增。
timezone.
utcoffset
(
dt
)
¶
Return the fixed value specified when the
timezone
instance is constructed. The
dt
argument is ignored. The return value is a
timedelta
instance equal to the difference between the local time and UTC.
timezone.
tzname
(
dt
)
¶
Return the fixed value specified when the
timezone
instance is constructed. If
name
is not provided in the constructor, the name returned by
tzname(dt)
is generated from the value of the
offset
as follows. If
offset
is
timedelta(0)
, the name is “UTC”, otherwise it is a string ‘UTC±HH:MM’, where ± is the sign of
offset
, HH and MM are two digits of
offset.hours
and
offset.minutes
分别。
3.6 版改变：
Name generated from
offset=timedelta(0)
is now plain ‘UTC’, not ‘UTC+00:00’.
timezone.
dst
(
dt
)
¶
总是返回
None
.
timezone.
fromutc
(
dt
)
¶
返回
dt
+
offset
。
dt
argument must be an aware
datetime
instance, with
tzinfo
设为
self
.
类属性：
timezone.
utc
¶
The UTC timezone,
timezone(timedelta(0))
.
strftime()
and
strptime()
Behavior
¶
date
,
datetime
，和
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
time
module’s
time.strftime(fmt,
d.timetuple())
although not all objects support a
timetuple()
方法。
Conversely, the
datetime.strptime()
class method creates a
datetime
object from a string representing a date and time and a corresponding format string.
datetime.strptime(date_string,
format)
相当于
datetime(*(time.strptime(date_string,
format)[0:6]))
, except when the format includes sub-second components or timezone offset information, which are supported in
datetime.strptime
but are discarded by
time.strptime
.
For
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
1
for the month and day.
For
date
objects, the format codes for hours, minutes, seconds, and microseconds should not be used, as
date
objects have no such values. If they’re used anyway,
0
is substituted for them.
The full set of format codes supported varies across platforms, because Python calls the platform C library’s
strftime()
function, and platform variations are common. To see the full set of format codes supported on your platform, consult the
strftime(3)
文档编制。
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.
| 指令 | 含义 | 范例 | 注意事项 |
|---|---|---|---|
%a
|
Weekday as locale’s abbreviated name. |
Sun, Mon, …, Sat (en_US);
So, Mo, …, Sa (de_DE)
|
(1) |
%A
|
Weekday as locale’s full name. |
Sunday, Monday, …, Saturday (en_US);
Sonntag, Montag, …, Samstag (de_DE)
|
(1) |
%w
|
Weekday as a decimal number, where 0 is Sunday and 6 is Saturday. | 0, 1, …, 6 | |
%d
|
Day of the month as a zero-padded decimal number. | 01, 02, …, 31 | |
%b
|
Month as locale’s abbreviated name. |
Jan, Feb, …, Dec (en_US);
Jan, Feb, …, Dez (de_DE)
|
(1) |
%B
|
Month as locale’s full name. |
January, February, …, December (en_US);
Januar, Februar, …, Dezember (de_DE)
|
(1) |
%m
|
Month as a zero-padded decimal number. | 01, 02, …, 12 | |
%y
|
Year without century as a zero-padded decimal number. | 00, 01, …, 99 | |
%Y
|
Year with century as a decimal number. | 0001, 0002, …, 2013, 2014, …, 9998, 9999 | (2) |
%H
|
Hour (24-hour clock) as a zero-padded decimal number. | 00, 01, …, 23 | |
%I
|
Hour (12-hour clock) as a zero-padded decimal number. | 01, 02, …, 12 | |
%p
|
Locale’s equivalent of either AM or PM. |
AM, PM (en_US);
am, pm (de_DE)
|
(1), (3) |
%M
|
Minute as a zero-padded decimal number. | 00, 01, …, 59 | |
%S
|
Second as a zero-padded decimal number. | 00, 01, …, 59 | (4) |
%f
|
Microsecond as a decimal number, zero-padded on the left. | 000000, 000001, …, 999999 | (5) |
%z
|
UTC offset in the form +HHMM or -HHMM (empty string if the object is naive). | (empty), +0000, -0400, +1030 | (6) |
%Z
|
Time zone name (empty string if the object is naive). | (empty), UTC, EST, CST | |
%j
|
Day of the year as a zero-padded decimal number. | 001, 002, …, 366 | |
%U
|
Week number of the year (Sunday as the first day of the week) as a zero padded decimal number. All days in a new year preceding the first Sunday are considered to be in week 0. | 00, 01, …, 53 | (7) |
%W
|
Week number of the year (Monday as the first day of the week) as a decimal number. All days in a new year preceding the first Monday are considered to be in week 0. | 00, 01, …, 53 | (7) |
%c
|
Locale’s appropriate date and time representation. |
Tue Aug 16 21:30:00 1988 (en_US);
Di 16 Aug 21:30:00 1988 (de_DE)
|
(1) |
%x
|
Locale’s appropriate date representation. |
08/16/88 (None);
08/16/1988 (en_US);
16.08.1988 (de_DE)
|
(1) |
%X
|
Locale’s appropriate time representation. |
21:30:00 (en_US);
21:30:00 (de_DE)
|
(1) |
%%
|
A literal
'%'
character.
|
% |
Several additional directives not required by the C89 standard are included for convenience. These parameters all correspond to ISO 8601 date values. These may not be available on all platforms when used with the
strftime()
method. The ISO 8601 year and ISO 8601 week directives are not interchangeable with the year and week number directives above. Calling
strptime()
with incomplete or ambiguous ISO 8601 directives will raise a
ValueError
.
| 指令 | 含义 | 范例 | 注意事项 |
|---|---|---|---|
%G
|
ISO 8601 year with century representing the year that contains the greater part of the ISO week (
%V
).
|
0001, 0002, …, 2013, 2014, …, 9998, 9999 | (8) |
%u
|
ISO 8601 weekday as a decimal number where 1 is Monday. | 1, 2, …, 7 | |
%V
|
ISO 8601 week as a decimal number with Monday as the first day of the week. Week 01 is the week containing Jan 4. | 01, 02, …, 53 | (8) |
3.6 版新增：
%G
,
%u
and
%V
被添加。
注意事项：
Because the format depends on the current locale, care should be taken when making assumptions about the output value. Field orderings will vary (for example, “month/day/year” versus “day/month/year”), and the output may contain Unicode characters encoded using the locale’s default encoding (for example, if the current locale is
ja_JP
, the default encoding could be any one of
eucJP
,
SJIS
，或
utf-8
; use
locale.getlocale()
to determine the current locale’s encoding).
strptime()
method can parse years in the full [1, 9999] range, but years < 1000 must be zero-filled to 4-digit width.
3.2 版改变：
In previous versions,
strftime()
method was restricted to years >= 1900.
3.3 版改变：
In version 3.2,
strftime()
method was restricted to years >= 1000.
When used with the
strptime()
method, the
%p
directive only affects the output hour field if the
%I
directive is used to parse the hour.
不像
time
module, the
datetime
module does not support leap seconds.
When used with the
strptime()
method, 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).
For a naive object, the
%z
and
%Z
format codes are replaced by empty strings.
For an aware object:
%z
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
utcoffset()
返回
timedelta(hours=-3,
minutes=-30)
,
%z
is replaced with the string
'-0330'
.
%Z
若
tzname()
返回
None
,
%Z
is replaced by an empty string. Otherwise
%Z
is replaced by the returned value, which must be a string.
When used with the
strptime()
method,
%U
and
%W
are only used in calculations when the day of the week and the calendar year (
%Y
) are specified.
类似
%U
and
%W
,
%V
is only used in calculations when the day of the week and the ISO year (
%G
) are specified in a
strptime()
format string. Also note that
%G
and
%Y
are not interchangeable.
脚注
| [1] | If, that is, we ignore the effects of Relativity |