chapter-8.3-datetime.md

Chapter 8.3 The datetime module

Table of Contents:

• Chapter 8.3 The datetime module
  • datetime Constants
  • datetime Data types
    • 1. class datetime.date
    • 2. class datetime.time
    • 3. class datetime.datetime
    • 4. class datetime.timedelta
    • 5. class datetime.tzinfo
    • 6. class datetime.timezone
  • Datetime Operations
    • Adding timedelta to thedatetime instance.
    • Subtracting two datetime instances
  • Parsing and formatting datetime strings
    • Parsing a datetime string
    • Formatting a datetime string
    • Some useful datetime formatting codes:

Reference: https://docs.python.org/3/library/datetime.html

The datetime module supplies different classes for manipulating date and time instances. We can perform different mathematical operations

datetime Constants

The datetime module exports following constants.

• datetime.MINYEAR: 1
• datetime.MAXYEAR: 9999

datetime Data types

The datetime module exports following data types:

1. class datetime.date

The datetime.date class can create a date object that accepts 3 parameters, i.e. year, month, and day as numbers to instantiate the date object.

initializing date object

from datetime import date

date_1 = date(1999, 12, 31)  # 1999-12-31
date_2 = date(year=1999, month=12, day=31)

2. class datetime.time

The datetime.time class accepts hour, minute, second, microsecond, tzinfo (optional) parameters that has default values of 0. the datetime.time class creates time object.

initializing time object

from datetime import time

time1 = time(hour=5)  # 05:00:00
time2 = time(hour=5, minute=50)  # 05:50:00
time3 = time(hour=5, minute=50, second=30)  # 05:50:30
time4 = time(hour=5, minute=50, second=30, microsecond=100)  # 05:50:30.000100

3. class datetime.datetime

The class datetime.datetime is a combination of datetime.date and datetime.time classes. It can accept all attributes of both date, and time objects. the parameters of datetime class are as follows:

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 tzinfo subclass. The remaining arguments may be ints and has default value 0.

initializing datetime object

from datetime import datetime

datetime_1 = datetime(1999, 12, 31, 23, 59, 59, 100)  # 1999-12-31 23:59:59.000100

4. class datetime.timedelta

A datetime.timedelta class is a duration of time that expresses the difference between two date, time, or datetime instances to microsecond resolution

**initializing the timedelta object

from datetime import timedelta

d1 = timedelta(hours=10)
d2 = timedelta(days=30, hours=20, minutes=50, seconds=30)  # 30 days, 20:50:30

5. class datetime.tzinfo

tzinfo is an abstract base class for time zone information objects. these are used by the datetime and time class to provide ta customizable notion of time adjustment.

6. class datetime.timezone

timezone class is a class that implements tzinfo abstract base class that has a fixed offset from the UTC.

from datetime import timezone, timedelta

tz1 = timezone(offset=timedelta(hours=5, minutes=45))

Datetime Operations

Adding timedelta to thedatetime instance

We can add timedelta value to date or datetime instance to get the new date or datetime.

from datetime import date, datetime, timedelta

date_1 = date(1999, 12, 31)
date_2 = date_1 + timedelta(days=5)  # 2000-01-05

datetime_1 = datetime(1999, 12, 31, 12, 30, 50)

datetime_2 = datetime_1 + timedelta(days=5, hours=10)  # 2000-01-05 22:30:50

Note: we cannot add two date or datetime instances to get a new date or datetime instance.

Subtracting two datetime instances

We can subtract one date or datetime instance from another date or datetime instance to get the time difference as timedelta instance.

from datetime import date, datetime

date_1 = date(1999, 12, 31)
date_2 = date(1999, 10, 15)
diff_1 = date_1 - date_2  # 77 days, 0:00:00

datetime_1 = datetime(1999, 12, 31, 12, 30, 50)
datetime_2 = datetime(1999, 10, 15, 19, 45, 21)
diff_2 = datetime_1 - datetime_2  # 76 days, 16:45:29

Note: Subtracting two date or datetime instances always give timedelta instance.

Parsing and formatting datetime strings

Parsing a datetime string

We can parse a datetime string by using datetime.strptime() method. the strptime() method takes 2 arguments date_string and format to parse the string.

from datetime import datetime

datetime = datetime.strptime('1999/12/31', '%Y/%m/%d')  # 1999-12-31 00:00:00

Formatting a datetime string

We can format a date or datetime instance to a datetime string by using datetime.strftime() method.

from datetime import date, datetime

d1 = date(1999, 12, 31)
d_str = d1.strftime('%Y/%m/%d')  # 1999/12/31
d_str2 = d1.strftime('%b %d, %Y')  # Dec 31, 1999

dt1 = datetime(1999, 12, 31, 23, 59, 30)
dt_str = dt1.strftime('%Y/%m/%d, %HH:%MM:%SS')  # 1999/12/31, 23H:59M:30S

Some useful datetime formatting codes

• %a: Weekday abbreviated name (Sun, Mon, ..., Sat)
• %A: Weekday full name (Sunday, Monday, ..., Saturday)
• %d: Day of the month (01, 02, ..., 31)
• %b: Month abbreviated name (Jan, Feb, ..., Dec)
• %B: Month full name (January, February, ..., December)
• %m: Month as number (01, 02, ..., 12)
• %Y: Year with Century (1999, 2000, ...)
• %H: 24-Hour Clock (00, 01, ..., 23)
• %M: Minutes (00, 01, ..., 59)
• %S: Seconds (00, 01, ..., 59)

For more formatting options, we can check out https://docs.python.org/3/library/datetime.html#strftime-and-strptime-format-codes.