Instantiation in Python

Definition

Instantiation is the process of creating an instance of a class in Python. This is achieved by calling a class constructor, such as list() or dict(), to create objects of built-in classes. When you instantiate a class, you are essentially creating an object that is a specific realization of that class.

Overview

The instantiation process involves calling the class constructor, which initializes the instance with specific attributes. This process is fundamental in object-oriented programming as it allows for the creation of objects that can have their own unique data and behavior, defined by the class.

Detailed Process

When a class is instantiated, the constructor is called, which triggers two special methods: __new__ and __init__. The __new__ method is responsible for creating a new instance of the class, while the __init__ method initializes the instance with the desired attributes and any additional setup required.

Figure: Instantiation Process

Figure 10.2 The instantiation process of a custom class. After we call the constructor of a custom class, behind the scenes, the new and init methods are invoked sequentially, with new creating the new object and init completing the initialization process. In the end, the construction results in the creation of an instance object.

Examples

Example 1: Instantiating a Custom Class

Consider the following example where we create an instance of a custom class Task:

task = Task("Laundry", "Wash clothes", 3)

In this example, task is an instance of the Task class, initialized with specific attributes: a name (“Laundry”), a description (“Wash clothes”), and a priority level (3).

Example 2: Simplified Instantiation

Another example of instantiation is:

task = Task("Laundry")

Here, the Task class is instantiated with only the name attribute "Laundry". The constructor is called, which triggers the __new__ and __init__ methods to create and initialize the object.