In this notebook, we are going to discuss the datetime module, it's functionality, uses and it's pros and cons.
The datetime module provides classes for manipulating dates and times. There can be numerous applications that require processing dates and times. The datetime module is very useful for dealing with different types of dates and times format.
The date and time objects can be either categorized as aware or naive depending on whether or not they include timezone information.
An aware object can identify itself relative to other time objects with the help of other parameters such as timezone and daylight saving information.
A naive object on the other hand doesn't contain enough information to identify itself to other date/time objects.
Datetime objects have an optional timezone information attribute tzinfo which we will cover later. The tzinfo lets us handle offset from UTC time, timezone name and whether daylight saving time is in effect.
Let us import the datetime module and try few examples to illustrate how it works.
import datetime
By default, datetime.time assumes standard time conditions that is every day has 24*60*60 seconds. The attributes availabe for this class are:
- hour
- minute
- second
- microsecond
- tzinfo
Similarly datetime.date by default assumes Georgian calendar. The attributes for this class are:
- year
- month
- day
A combination of date and time. The attributes for this class are:
- year
- month
- day
- hour
- minute
- second
- microsecond
- tzinfo
This is one of the most commonly used classes of the datetime module. The timedelta class enables us to calculate the difference between date, time and datetime object.
It is an abstract base class for timezone information. It is used to provide more control over timezones.
This is a class that implements the tzinfo abstract base class as a fixed offset from the UTC. It is mainly used for tzinfo because it maps the timezone to the UTC difference.
datetime_object = datetime.datetime.now()
print(datetime_object)
print("Year: ", datetime_object.year)
print("Month: ", datetime_object.month)
print("Dat: ", datetime_object.day)
print("Hour: ", datetime_object.hour)
print("Minute: ", datetime_object.minute)
print("Second: ", datetime_object.second)
print("TimeZone info: ", datetime_object.tzinfo)
In the previous example note that the timezone info is none, this is due to the fact that we didn't make our datetime object time zone aware. Let us fix this by applying some changes...
datetime_object = datetime.datetime.now()
# we will use the timezone class mentioned above in the
# available data types of the datetime module
datetime_object = datetime_object.replace(tzinfo=datetime.timezone.utc)
print(datetime_object)
print("Year: ", datetime_object.year)
print("Month: ", datetime_object.month)
print("Dat: ", datetime_object.day)
print("Hour: ", datetime_object.hour)
print("Minute: ", datetime_object.minute)
print("Second: ", datetime_object.second)
print("TimeZone info: ", datetime_object.tzinfo)
Now you can see that the affiliated timezone with the datetime object we created is set to UTC. We can also convert this datetime object to a more readable format using the isoformat method.
print(datetime_object.isoformat())
In case we want to use a different timezone than UTC, we can use the pytz module as shown below.
import pytz
# print(pytz.all_timezones_set)
new_timezone = pytz.timezone('Europe/Madrid')
datetime_object = datetime.datetime.now(tz=new_timezone)
# print(datetime_object)
print("Year: ", datetime_object.year)
print("Month: ", datetime_object.month)
print("Dat: ", datetime_object.day)
print("Hour: ", datetime_object.hour)
print("Minute: ", datetime_object.minute)
print("Second: ", datetime_object.second)
print("TimeZone info: ", datetime_object.tzinfo)
print(datetime_object.isoformat())
day = datetime.date.today()
print(day)
day = datetime.date(2020, 8, 23)
print(day)
Getting a date from a timestamp
A Unix timestamp is a number of seconds in UTC format between a particular date and January 1, 1970 at UTC. It's a very standard way of dealing with datetime objects.
The current timestamp at the moment of writing this notebook is: 1629516295 so let us explore how to extract information from this timestamp using datetime module.
timestamp = 1629516295
datetime_object = datetime.datetime.fromtimestamp(timestamp)
# We also know that Unix timestamps are in UTC so we might as well
# add the timezone info to our object.
datetime_object = datetime_object.replace(tzinfo=datetime.timezone.utc)
print(datetime_object)
print("Year: ", datetime_object.year)
print("Month: ", datetime_object.month)
print("Dat: ", datetime_object.day)
print("Hour: ", datetime_object.hour)
print("Minute: ", datetime_object.minute)
print("Second: ", datetime_object.second)
print("TimeZone info: ", datetime_object.tzinfo)
datetime_object = datetime.datetime.now()
print("Timestamp: ", datetime_object.timestamp())
As explained earlier, timedelta can be used to represent difference between two dates or times which might come in handy in a lot of situations. Let us explore the following example.
Count the number of days between 24-07-2020 and 26-03-2021.
start_date = datetime.date(2020, 7, 24)
end_date = datetime.date(2021, 3, 26)
# We can simply just subtract these two objects and the result would be
# a timedelta object
timedelta = end_date - start_date
print(type(timedelta))
print("Day difference: ", timedelta.days)
Let's explore another example...
What will be the date if we add 28 days to todays date.
today = datetime.date.today()
timedelta_needed = datetime.timedelta(days=28)
result_date = today + timedelta_needed
print(result_date)
The datetime module contains a very powerful method called strftime which helps us format the dates in whichever format we need.
# current date and time
now = datetime.datetime.now(tz=pytz.timezone('UTC'))
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("mm/dd/YY:", s1)
s2 = now.strftime("%d/%m/%Y, %H:%M:%S")
# dd/mm/YY H:M:S format
print("dd/mm/YY:", s2)
# Timezone
print("Timezone: ", now.strftime("%Z"))
# Weekday
print("Weekday: ", now.strftime("%A"))
# Abbreviated weekday
print("Abbreviated Weekday: ", now.strftime("%a"))
# Locale's appropriate date and time representation
print("Locale representation: ", now.strftime("%c"))
This is a link to a cheatsheet containing all available formats we can utilize to view our dates and/or times...
https://www.nbshare.io/notebook/510557327/Strftime-and-Strptime-In-Python/
As opposed to the strftime method, the strptime method takes in a string and converts it into datetime object. This method takes two paramaters. These are:
- Date string
- Date Format
The second parameter (format) is referring to the format directives. The same ones we used in strftime ('%A, %d, %Z .. etc.). It acts in the way that tells Strptime what is the format of the datetime string to be processed. Now let us work on few examples.
import datetime
datetime_string = '08/23/21 15:23:52'
datetime_object = datetime.datetime.strptime(datetime_string, '%m/%d/%y %H:%M:%S')
print(type(datetime_object))
print(datetime_object)
As you can see in the example above, the returned type is a datetime object and therefore we can manipulate it however we want using all the datetime modules classes and methods available. Let us work on few more examples to consolidate our understanding for this method.
datetime_string = '08/23/21 15:23:52'
date_object = datetime.datetime.strptime(datetime_string, '%m/%d/%y %H:%M:%S').date()
print(type(date_object))
print(date_object)
time_object = datetime.datetime.strptime(datetime_string, '%m/%d/%y %H:%M:%S').time()
print(type(time_object))
print(time_object)
# Notice below how the time representation has changed from the above example
# and that we now have a double colons. Observe how will we adjust the format
# of the strptime method so as to correctly parse the input string.
time_example = '15::23::26'
time_example_object = datetime.datetime.strptime(time_example, '%H::%M::%S')
print(type(time_example_object))
print(time_example_object)
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