V tomto článku sa naučíte manipulovať s dátumom a časom v Pythone pomocou príkladov.
Python má modul s názvom datetime, ktorý pracuje s dátumami a časmi. Vytvorme niekoľko jednoduchých programov týkajúcich sa dátumu a času, skôr ako sa pustíme do hĺbky.
Príklad 1: Získajte aktuálny dátum a čas
import datetime datetime_object = datetime.datetime.now() print(datetime_object)
Keď spustíte program, výstup bude asi ako:
2018-12-19 09: 26: 03.478039
Tu sme pomocou príkazu importovali modul datetimeimport datetime .
Jednou z tried definovaných v datetimemodule je datetimeclass. Potom sme pomocou now()metódy vytvorili datetimeobjekt obsahujúci aktuálny miestny dátum a čas.
Príklad 2: Získajte aktuálny dátum
import datetime date_object = datetime.date.today() print(date_object)
Keď spustíte program, výstup bude asi ako:
19. 12. 2018
V tomto programe sme použili today()metódu definovanú v datetriede na získanie dateobjektu obsahujúceho aktuálny lokálny dátum.
Čo je vo vnútri datetime?
Pomocou funkcie dir () môžeme získať zoznam obsahujúci všetky atribúty modulu.
import datetime print(dir(datetime))
Po spustení programu bude výstup:
('MAXYEAR', 'MINYEAR', '__builtins__', '__cached__', '__doc__', '__file__', '__loader__', '__name__', '__package__', '__spec__', '_divide_and_round', 'date', ' datetime ',' datetime_CAPI ',' time ',' timedelta ',' timezone ',' tzinfo ')
Bežne používané triedy v module datetime sú:
- dátum Trieda
- časová trieda
- trieda datetime
- trieda timedelta
datetime.date Trieda
Môžete vytvoriť inštanciu dateobjektov z datetriedy. Objekt dátumu predstavuje dátum (rok, mesiac a deň).
Príklad 3: Objekt dátumu, ktorý predstavuje dátum
import datetime d = datetime.date(2019, 4, 13) print(d)
Po spustení programu bude výstup:
2019-04-13
Ak vás zaujíma, date()vo vyššie uvedenom príklade je konštruktér datetriedy. Konštruktor berie tri argumenty: rok, mesiac a deň.
Premenná a je dateobjekt.
dateTriedu môžeme importovať iba z datetimemodulu. Tu je postup:
from datetime import date a = date(2019, 4, 13) print(a)
Príklad 4: Získajte aktuálny dátum
dateObjekt obsahujúci aktuálny dátum môžete vytvoriť pomocou metódy triedy s názvom today(). Tu je postup:
from datetime import date today = date.today() print("Current date =", today)
Príklad 5: Získajte dátum z časovej pečiatky
Môžeme tiež vytvárať dateobjekty z časovej pečiatky. Časová známka Unixu je počet sekúnd medzi konkrétnym dátumom a 1. januárom 1970 v UTC. Môžete previesť časovú pečiatku na dátum pomocou fromtimestamp()metódy.
from datetime import date timestamp = date.fromtimestamp(1326244364) print("Date =", timestamp)
Po spustení programu bude výstup:
Dátum = 11.01.2012
Príklad 6: Vytlačte si dnešný rok, mesiac a deň
We can get year, month, day, day of the week etc. from the date object easily. Here's how:
from datetime import date # date object of today's date today = date.today() print("Current year:", today.year) print("Current month:", today.month) print("Current day:", today.day)
datetime.time
A time object instantiated from the time class represents the local time.
Example 7: Time object to represent time
from datetime import time # time(hour = 0, minute = 0, second = 0) a = time() print("a =", a) # time(hour, minute and second) b = time(11, 34, 56) print("b =", b) # time(hour, minute and second) c = time(hour = 11, minute = 34, second = 56) print("c =", c) # time(hour, minute, second, microsecond) d = time(11, 34, 56, 234566) print("d =", d)
When you run the program, the output will be:
a = 00:00:00 b = 11:34:56 c = 11:34:56 d = 11:34:56.234566
Example 8: Print hour, minute, second and microsecond
Once you create a time object, you can easily print its attributes such as hour, minute etc.
from datetime import time a = time(11, 34, 56) print("hour =", a.hour) print("minute =", a.minute) print("second =", a.second) print("microsecond =", a.microsecond)
When you run the example, the output will be:
hour = 11 minute = 34 second = 56 microsecond = 0
Notice that we haven't passed microsecond argument. Hence, its default value 0 is printed.
datetime.datetime
The datetime module has a class named dateclass that can contain information from both date and time objects.
Example 9: Python datetime object
from datetime import datetime #datetime(year, month, day) a = datetime(2018, 11, 28) print(a) # datetime(year, month, day, hour, minute, second, microsecond) b = datetime(2017, 11, 28, 23, 55, 59, 342380) print(b)
When you run the program, the output will be:
2018-11-28 00:00:00 2017-11-28 23:55:59.342380
The first three arguments year, month and day in the datetime() constructor are mandatory.
Example 10: Print year, month, hour, minute and timestamp
from datetime import datetime a = datetime(2017, 11, 28, 23, 55, 59, 342380) print("year =", a.year) print("month =", a.month) print("hour =", a.hour) print("minute =", a.minute) print("timestamp =", a.timestamp())
When you run the program, the output will be:
year = 2017 month = 11 day = 28 hour = 23 minute = 55 timestamp = 1511913359.34238
datetime.timedelta
A timedelta object represents the difference between two dates or times.
Example 11: Difference between two dates and times
from datetime import datetime, date t1 = date(year = 2018, month = 7, day = 12) t2 = date(year = 2017, month = 12, day = 23) t3 = t1 - t2 print("t3 =", t3) t4 = datetime(year = 2018, month = 7, day = 12, hour = 7, minute = 9, second = 33) t5 = datetime(year = 2019, month = 6, day = 10, hour = 5, minute = 55, second = 13) t6 = t4 - t5 print("t6 =", t6) print("type of t3 =", type(t3)) print("type of t6 =", type(t6))
When you run the program, the output will be:
t3 = 201 days, 0:00:00 t6 = -333 days, 1:14:20 type of t3 = type of t6 =
Notice, both t3 and t6 are of type.
Example 12: Difference between two timedelta objects
from datetime import timedelta t1 = timedelta(weeks = 2, days = 5, hours = 1, seconds = 33) t2 = timedelta(days = 4, hours = 11, minutes = 4, seconds = 54) t3 = t1 - t2 print("t3 =", t3)
When you run the program, the output will be:
t3 = 14 days, 13:55:39
Here, we have created two timedelta objects t1 and t2, and their difference is printed on the screen.
Example 13: Printing negative timedelta object
from datetime import timedelta t1 = timedelta(seconds = 33) t2 = timedelta(seconds = 54) t3 = t1 - t2 print("t3 =", t3) print("t3 =", abs(t3))
When you run the program, the output will be:
t3 = -1 day, 23:59:39 t3 = 0:00:21
Example 14: Time duration in seconds
You can get the total number of seconds in a timedelta object using total_seconds() method.
from datetime import timedelta t = timedelta(days = 5, hours = 1, seconds = 33, microseconds = 233423) print("total seconds =", t.total_seconds())
When you run the program, the output will be:
total seconds = 435633.233423
You can also find sum of two dates and times using + operator. Also, you can multiply and divide a timedelta object by integers and floats.
Python format datetime
The way date and time is represented may be different in different places, organizations etc. It's more common to use mm/dd/yyyy in the US, whereas dd/mm/yyyy is more common in the UK.
Python has strftime() and strptime() methods to handle this.
Python strftime() - datetime object to string
The strftime() method is defined under classes date, datetime and time. The method creates a formatted string from a given date, datetime or time object.
Example 15: Format date using strftime()
from datetime import datetime # current date and time now = datetime.now() t = now.strftime("%H:%M:%S") print("time:", t) s1 = now.strftime("%m/%d/%Y, %H:%M:%S") # mm/dd/YY H:M:S format print("s1:", s1) s2 = now.strftime("%d/%m/%Y, %H:%M:%S") # dd/mm/YY H:M:S format print("s2:", s2)
When you run the program, the output will be something like:
time: 04:34:52 s1: 12/26/2018, 04:34:52 s2: 26/12/2018, 04:34:52
Here, %Y, %m, %d, %H etc. are format codes. The strftime() method takes one or more format codes and returns a formatted string based on it.
In the above program, t, s1 and s2 are strings.
%Y- year (0001,… , 2018, 2019,… , 9999)%m- month (01, 02,… , 11, 12)%d- day (01, 02,… , 30, 31)%H- hour (00, 01,… , 22, 23%M- minute (00, 01,… , 58, 59)%S- second (00, 01,… , 58, 59)
To learn more about strftime() and format codes, visit: Python strftime().
Python strptime() - string to datetime
The strptime() method creates a datetime object from a given string (representing date and time).
Example 16: strptime()
from datetime import datetime date_string = "21 June, 2018" print("date_string =", date_string) date_object = datetime.strptime(date_string, "%d %B, %Y") print("date_object =", date_object)
When you run the program, the output will be:
date_string = 21 June, 2018 date_object = 2018-06-21 00:00:00
The strptime() method takes two arguments:
- reťazec predstavujúci dátum a čas
- formátový kód ekvivalentný prvému argumentu
Mimochodom %d, %Ba %Ykódy formátu sa používajú pre deň, mesiac (celé meno) a rok.
Navštívte stránku Python strptime () a dozviete sa viac.
Spracovanie časovej zóny v Pythone
Predpokladajme, že pracujete na projekte a musíte zobraziť dátum a čas na základe ich časového pásma. Namiesto pokusu o časové pásmo sami vám odporúčame použiť modul pytZ od iného výrobcu.
from datetime import datetime import pytz local = datetime.now() print("Local:", local.strftime("%m/%d/%Y, %H:%M:%S")) tz_NY = pytz.timezone('America/New_York') datetime_NY = datetime.now(tz_NY) print("NY:", datetime_NY.strftime("%m/%d/%Y, %H:%M:%S")) tz_London = pytz.timezone('Europe/London') datetime_London = datetime.now(tz_London) print("London:", datetime_London.strftime("%m/%d/%Y, %H:%M:%S"))
Keď spustíte program, výstup bude asi ako:
Miestny čas: 2018-12-20 13:10: 44.260462 Amerika / Nový_York čas: 2018-12-20 13:10: 44.260462 Európa / Londýn čas: 2018-12-20 13:10: 44.260462
Tu sú datetime_NY a datetime_London objekty datetime obsahujúce aktuálny dátum a čas ich príslušného časového pásma.
