16.11. 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.
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. We have not passed any
parameters to the constructor. When the constructor returns, we use the variable `` stuff`` to point to the returned instance of the list class.
The second and third lines call 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.
We then print out the first item in the list using the square brackets which are
a shortcut to calling the __getitem method within the `` stuff`` . This
is equivalent to calling the getitem__ method in the `` list`` class
and passing the `` stuff`` object 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 that the object can clean up any
loose ends as necessary.
Those are the basics 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.^[If
you are curious about where the list class is defined, take a look
at (hopefully the URL won’t change)
https://github.com/python/cpython/blob/master/Objects/listobject.c -
the list class is written in a language
called “C”. If you take a look at that source code and find it curious
you might want to explore a few Computer Science courses.]