datetime - time, date, date+time

Разбор и представление даты и времени, арифметические операции над ними, сравнение.

datetime.time - чисто время (часы, минуты, секунды, милисекунды, таймзона)

Только время без даты.

import datetime

t = datetime.time(1, 2, 3)
print(t)
print('hour       :', t.hour)
print('minute     :', t.minute)
print('second     :', t.second)
print('microsecond:', t.microsecond)
print('tzinfo     :', t.tzinfo)

получим:

01:02:03
hour       : 1
minute     : 2
second     : 3
microsecond: 0
tzinfo     : None

Диапазон данных:

import datetime

print('Earliest  :', datetime.time.min)
print('Latest    :', datetime.time.max)
print('Resolution:', datetime.time.resolution)

получим:

Earliest  : 00:00:00
Latest    : 23:59:59.999999
Resolution: 0:00:00.000001

Время не может устанавливаться точнее, чем в милисекундах.

import datetime

for m in [1, 0, 0.1, 0.6]:
    try:
        print('{:02.1f} :'.format(m),
              datetime.time(0, 0, 0, microsecond=m))
    except TypeError as err:
        print('ERROR:', err)

получим:

1.0 : 00:00:00.000001
0.0 : 00:00:00
ERROR: integer argument expected, got float
ERROR: integer argument expected, got float

datetime.date - дни, месяцы, года

import datetime

today = datetime.date.today()
print(today)
print('ctime  :', today.ctime())
tt = today.timetuple()
print('tuple  : tm_year  =', tt.tm_year)
print('         tm_mon   =', tt.tm_mon)
print('         tm_mday  =', tt.tm_mday)
print('         tm_hour  =', tt.tm_hour)
print('         tm_min   =', tt.tm_min)
print('         tm_sec   =', tt.tm_sec)
print('         tm_wday  =', tt.tm_wday)
print('         tm_yday  =', tt.tm_yday)
print('         tm_isdst =', tt.tm_isdst)
print('ordinal:', today.toordinal())
print('Year   :', today.year)
print('Mon    :', today.month)
print('Day    :', today.day)

получаем:

2018-04-19
ctime  : Thu Apr 19 00:00:00 2018
tuple  : tm_year  = 2018
         tm_mon   = 4
         tm_mday  = 19
         tm_hour  = 0
         tm_min   = 0
         tm_sec   = 0
         tm_wday  = 3
         tm_yday  = 109
         tm_isdst = -1
ordinal: 736803
Year   : 2018
Mon    : 4
Day    : 19

ordinal - количество дней с 1 января 1 года.

import datetime
import time

o = 736803
print('o               :', o)
print('fromordinal(o)  :', datetime.date.fromordinal(o))

t = time.time()
print('t               :', t)
print('fromtimestamp(t):', datetime.date.fromtimestamp(t))

получаем:

o               : 736803
fromordinal(o)  : 2018-04-19
t               : 1524125286.857128
fromtimestamp(t): 2018-04-19

Диапазон date

import datetime

print('Earliest  :', datetime.date.min)
print('Latest    :', datetime.date.max)
print('Resolution:', datetime.date.resolution)

получаем:

Earliest  : 0001-01-01
Latest    : 9999-12-31
Resolution: 1 day, 0:00:00

Создадим дату в виде строки и заменим в строке год

import datetime

d1 = datetime.date(2008, 3, 29)
print('d1:', d1.ctime())

d2 = d1.replace(year=2009)
print('d2:', d2.ctime())

получим

d1: Sat Mar 29 00:00:00 2008
d2: Sun Mar 29 00:00:00 2009

Острожнее с таким заменами. Вы можете в дате 29 февраля високосного года заменить год на невисокосный. Что делать? Изменять год через timedelta.

datetime.timedelta - разница времен

Если объект datetime - время отправления и прибытия поезда (с датой!), то timedelta - время в пути.

import datetime

print('microseconds:', datetime.timedelta(microseconds=1))
print('milliseconds:', datetime.timedelta(milliseconds=1))
print('seconds     :', datetime.timedelta(seconds=1))
print('minutes     :', datetime.timedelta(minutes=1))
print('hours       :', datetime.timedelta(hours=1))
print('days        :', datetime.timedelta(days=1))
print('weeks       :', datetime.timedelta(weeks=1))

получим:

microseconds: 0:00:00.000001
milliseconds: 0:00:00.001000
seconds     : 0:00:01
minutes     : 0:01:00
hours       : 1:00:00
days        : 1 day, 0:00:00
weeks       : 7 days, 0:00:00

total_seconds() - длительность в секундах (большое число)

import datetime

for delta in [datetime.timedelta(microseconds=1),
              datetime.timedelta(milliseconds=1),
              datetime.timedelta(seconds=1),
              datetime.timedelta(minutes=1),
              datetime.timedelta(hours=1),
              datetime.timedelta(days=1),
              datetime.timedelta(weeks=1),
              ]:
    print('{:15} = {:8} seconds'.format(
        str(delta), delta.total_seconds())
    )

получим

0:00:00.000001  =    1e-06 seconds
0:00:00.001000  =    0.001 seconds
0:00:01         =      1.0 seconds
0:01:00         =     60.0 seconds
1:00:00         =   3600.0 seconds
1 day, 0:00:00  =  86400.0 seconds
7 days, 0:00:00 = 604800.0 seconds

Арифметические операции над временем

import datetime

today = datetime.date.today()
print('Today    :', today)

one_day = datetime.timedelta(days=1)
print('One day  :', one_day)

yesterday = today - one_day
print('Yesterday:', yesterday)

tomorrow = today + one_day
print('Tomorrow :', tomorrow)

print()
print('tomorrow - yesterday:', tomorrow - yesterday)
print('yesterday - tomorrow:', yesterday - tomorrow)

получим:

Today    : 2018-04-19
One day  : 1 day, 0:00:00
Yesterday: 2018-04-18
Tomorrow : 2018-04-20

tomorrow - yesterday: 2 days, 0:00:00
yesterday - tomorrow: -2 days, 0:00:00

Можно увеличить timedelta с помощью арифметических операций:

import datetime

one_day = datetime.timedelta(days=1)
print('1 day    :', one_day)
print('5 days   :', one_day * 5)
print('1.5 days :', one_day * 1.5)
print('1/4 day  :', one_day / 4)

# assume an hour for lunch
work_day = datetime.timedelta(hours=7)
meeting_length = datetime.timedelta(hours=1)
print('meetings per day :', work_day / meeting_length)

получим

1 day    : 1 day, 0:00:00
5 days   : 5 days, 0:00:00
1.5 days : 1 day, 12:00:00
1/4 day  : 6:00:00
meetings per day : 7.0

Сравнение времен

import datetime
import time

print('Times:')
t1 = datetime.time(12, 55, 0)
print('  t1:', t1)
t2 = datetime.time(13, 5, 0)
print('  t2:', t2)
print('  t1 < t2:', t1 < t2)

print()
print('Dates:')
d1 = datetime.date.today()
print('  d1:', d1)
d2 = datetime.date.today() + datetime.timedelta(days=1)
print('  d2:', d2)
print('  d1 > d2:', d1 > d2)

получаем

Times:
  t1: 12:55:00
  t2: 13:05:00
  t1 < t2: True

Dates:
  d1: 2018-04-19
  d2: 2018-04-20
  d1 > d2: False

Комбинируем дату и время

Класс datetime - и дата, и время вместе.

import datetime

print('Now    :', datetime.datetime.now())
print('Today  :', datetime.datetime.today())
print('UTC Now:', datetime.datetime.utcnow())
print()

FIELDS = [
    'year', 'month', 'day',
    'hour', 'minute', 'second',
    'microsecond',
]

d = datetime.datetime.now()
for attr in FIELDS:
    print('{:15}: {}'.format(attr, getattr(d, attr)))

получим

Now    : 2018-04-19 11:26:41.266448
Today  : 2018-04-19 11:26:41.266670
UTC Now: 2018-04-19 08:26:41.266753

year           : 2018
month          : 4
day            : 19
hour           : 11
minute         : 26
second         : 41
microsecond    : 267463

Есть так же fromordinal() и fromtimestamp()

import datetime

t = datetime.time(1, 2, 3)
print('t :', t)

d = datetime.date.today()
print('d :', d)

dt = datetime.datetime.combine(d, t)
print('dt:', dt)

получим:

t : 01:02:03
d : 2018-04-19
dt: 2018-04-19 01:02:03

Разбор строки и преобразование в строку

По умолчанию объект datetime представлен в ISO-8601 формате (YYYY-MM-DDTHH:MM:SS.mmmmmm).

strftime() - представим в виде строки, используя другие форматы. strptime() - из строки (parse) в объект datetime

import datetime

format = "%a %b %d %H:%M:%S %Y"

today = datetime.datetime.today()
print('ISO     :', today)

s = today.strftime(format)
print('strftime:', s)

d = datetime.datetime.strptime(s, format)
print('strptime:', d.strftime(format))

получим

ISO     : 2018-04-19 11:31:58.397024
strftime: Thu Apr 19 11:31:58 2018
strptime: Thu Apr 19 11:31:58 2018

format поддерживает форматирование datetime

import datetime

today = datetime.datetime.today()
print('ISO     :', today)
print('format(): {:%a %b %d %H:%M:%S %Y}'.format(today))

получим

ISO     : 2018-03-18 16:20:35.006116
format(): Sun Mar 18 16:20:35 2018

Что получим по каким форматам

если возьмем 5:00 PM January 13, 2016 in the US/Eastern time zone:

Таймзона

Within datetime, time zones are represented by subclasses of tzinfo. Since tzinfo is an abstract base class, applications need to define a subclass and provide appropriate implementations for a few methods to make it useful.

datetime does include a somewhat naive implementation in the class timezone that uses a fixed offset from UTC, and does not support different offset values on different days of the year, such as where daylight savings time applies, or where the offset from UTC has changed over time.

import datetime

min6 = datetime.timezone(datetime.timedelta(hours=-6))
plus6 = datetime.timezone(datetime.timedelta(hours=6))
d = datetime.datetime.now(min6)

print(min6, ':', d)
print(datetime.timezone.utc, ':',
      d.astimezone(datetime.timezone.utc))
print(plus6, ':', d.astimezone(plus6))

# convert to the current system timezone
d_system = d.astimezone()
print(d_system.tzinfo, '      :', d_system)

получим

UTC-06:00 : 2018-04-19 02:40:28.133666-06:00
UTC : 2018-04-19 08:40:28.133666+00:00
UTC+06:00 : 2018-04-19 14:40:28.133666+06:00
MSK       : 2018-04-19 11:40:28.133666+03:00

The third party module pytz is a better implementation for time zones. It supports named time zones, and the offset database is kept up to date as changes are made by political bodies around the world.