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Engineering LibreTexts

14.S: Object-Oriented Programming (Summary)

This is a very quick introduction to object-oriented programming that focuses mainly on terminology and the syntax of defining and using objects. Let's quickly review the code that we looked at in the beginning of the chapter. At this point you should fully understand what is going on.

stuff = list()
print (stuff[0])

print (stuff.__getitem__(0))
print (list.__getitem__(stuff,0))

# Code:

The first line constructs a list object. When Python creates the list object, it calls the constructor method (named __init__) to set up the internal data attributes that will be used to store the list data. Due to encapsulation we neither need to know, nor need to care about how these internal data attributes are arranged.

We are not passing any parameters to the constructor and when the constructor returns, we use the variable stuff to point to the returned instance of the list class.

The second and third lines are calling the append method with one parameter to add a new item at the end of the list by updating the attributes within stuff. Then in the fourth line, we call the sort method with no parameters to sort the data within the stuff object.

Then we print out the first item in the list using the square brackets which are a shortcut to calling the __getitem__ method within the stuff object. And this is equivalent to calling the __getitem__ method in the list class passing the stuff object in as the first parameter and the position we are looking for as the second parameter.

At the end of the program the stuff object is discarded but not before calling the destructor (named __del__) so the object can clean up any loose ends as necessary.

Those are the basics and terminology of object oriented programming. There are many additional details as to how to best use object oriented approaches when developing large applications and libraries that are beyond the scope of this chapter.3