Published: Modified: V1.17
python

Date objects in Python

In javaScript there is a built in Date class, so I would think that there should be something to that effect in python also. Well there is a few built in standard libraries actually it would seem and one such library is the datetime library. This library is a little different from the built in Date class that I am used to with javaScript, for one thing there is not just one class, but a few classes actually. There is a datetime class that seems to be similar the the Date class, but there is also a date class, and a timedelta class also.

1 - Basics of the datetime library

To start off with I think I should go over just a few very basic getting started examples of the datetime library. There are a number of ways to create an instance of the main datetime class in this library so maybe it is a good idea to start there. It might be called for to go over just a few simple basic examples of the other classes that there are to work with in the library, mainly the date, and timedelta classes.

1.1 - The datetime.now prop and the datetime class

The now method of the datetime class is one way to go about getting an instance of the datetime class of the current date, and time. The datetime class is one of actually several classes rather than just one that I am used to when it comes to working with the native Date class in javaScript.

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import datetime as date
 
d = date.datetime.now()
 
print(type(d).__name__)  # datetime
print(d.year)            # 2021
print(d.month)           # 1
print(d.day)             # 21
print(d)                 # 2021-01-21 15:27:49.097128

The datetime might be the best class to go with in most cases. Or at least I am saying that because I am so accustomed to working with just one class that can be used for date and time rather than having more than one class to work with. However there are a few other classes, methods of those classes, as well as static methods of such classes that I think I should at least touch base on when it comes to a basic example section.

1.2 - uisng the datetime class dirrectly

The now method of the datetime property of the datetime library will return an instance of the datetime class. However it will always return such a class instance for the current time. What if I want another such class instance that is at a point that in time that is before or after the current time? To create such a class instance I am going to want to use the datetime class directly.

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import datetime as date
 
d = date.datetime(2020, 4, 6, 10, 5, 0, 123456)
 
print(d) # 2020-04-06 10:05:00.123456

1.3 - Subtracting two datetime instances and the timedelta class

Just like in javaScript I can subtract two datetime instances to get a time difference, but that difference is not a number index value like with the javaScript Date Class. The result of such an operation in python with datetime instances at least is an instance of a timedelta class.

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import datetime as date
 
d1 = date.datetime(1983, 4, 6, 10, 5, 0, 0)
d2 = date.datetime(2010, 8, 22, 10, 5, 0, 0)
 
td = d2 - d1
 
print( type(td).__name__)  # timedelta
print( td.days )           # 10000

1.4 - The date class

The now method will just return an instance of datetime for the current time, to get a date object of a point in the past I will want to use the main date class to create such a date object.

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import datetime as date
 
d = date.date(2020, 1, 1)
 
print( type(d).__name__ ) # date
print(d)                  # 2020-01-01

2 - The time delta class

So as I have covered briefly in the first section there is a timedelta class that is a special class that represents a time difference between two dates rather than a specific point in time. This timedelta class can be created by subtractive two date or datetime instances, it can also be used to create a new instance of these classed by adding the delta to one of them as a starting point. So in this section I am going to go over some simple quick examples of these datetime class instances.

2.1 - create a timedelta with subtraction of dates, and use it to get a new date

In the basic section where I covered the time delta briefly one way to create an instance of a time delta is by subtractive two instances of a date. However I did not cover how to go about using an instance of this time delta class, so with that said one way to use a time delta is to just add or subtract a time delta to another distance of a date, or date time to get a new point in time in the form of a date or datetime class instance.

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import datetime as date
 
d1 = date.date(1999, 1, 20)
d2 = date.date(1999, 1, 21)
 
td = d2 - d1
print(type(td).__name__)
 
d3 = date.date(2021, 4, 5) + td
print(type(d3).__name__)    # date
print( d3 ) # 2021-04-06

2.2 - Create a timedelta will the class dirrectly

Although it is great that I can create timedelta instances by getting the difference between two dates, it would be nice to also be able to just create them directly. For this there is the timedelta class of the datetime module where I can just call the main constructor function and pass some arguments for days, or seconds. For example I can create a time delta class instance that is one billion seconds, and then I can add that difference to the date that i was born to get the date and time at which I turned on billion seconds old.

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import datetime as date
 
d1 = date.date(1999, 1, 20)
d2 = date.date(1999, 1, 21)
 
td = d2 - d1
print(type(td).__name__)
 
d3 = date.date(2021, 4, 5) + td
print(type(d3).__name__)    # date
print( d3 ) # 2021-04-06

3 - A closer look at the date class

Now that I have some basic examples out of the way there is taking a closer look at the date class. Like many other classes there are many useful methods that can be called off of an instance of a date object.

3.1 - year, month, and day props

There are properties for the year, month, and day of a date object.

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import datetime as date
 
d = date.date(2020, 4, 6)
print(d.year)  # 2020
print(d.month) # 4
print(d.day)   # 6
print(d)       # 2020-04-06

3.2 - to a tuple

The timetuple method of a date class instance can return a tuple of the properties of a date object. The tuple then can be looped over in a for loop.

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import datetime as date
 
d = date.date(2020, 4, 6)
t = d.timetuple()
 
for p in t:
    print(p, end='.')
# 2020.4.6.0.0.0.0.97.-1.

4 - Conclusion

The datetime library is then the first go to library when it comes to doing things that have to do with time in a python project, however it might not be the end of such tasks also. There are a few other standard libraries that seem to have to do with time, and I have not yet looked into what there might be to work with when it comes to user space projects. However thinking from my experience with javaScript those far this datetime library all ready seems more than enough to help me with at least most basic tasks that come to mind that have to do with time. In fact it goes beyond the Date class that I am used to so I find it more than enough actually.

I did not get around to writing about every little feature when it comes to the additional classes in the library that have to do with time zones, and the time of date alone. When I get around to editing this post at some point in the future there is of course expanding on thoses, but I think I would also like to create at least a few actually simple project examples also, and that might be a better move. When it comes to covering every little detail of where there is in terms of classes and functions there is always the official python docs after all.