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Practice

Defining the Beginning, End, and Behavior of Objects

In Python, a class is the blueprint for creating objects.

This lesson will cover constructors, destructors, and methods, which are essential components of a class.


Defining the Beginning with a Constructor​

A constructor is a method that is automatically called when an object is created.

In Python, the constructor is defined using __init__ and it initializes the object's initial state.

Defining a Constructor
class Car:
    # Define the constructor
    def __init__(self, brand, model, year):
        # Set the attributes of the object
        self.brand = brand
        self.model = model
        self.year = year
        print(f"{self.brand} {self.model} created")

# Create a car object with brand 'Lamboo', model 'Avent', and year 2021
lambo = Car("Lamboo", "Avent", 2021)
# Output: Lamboo Avent created

# Create a car object with brand 'Tesla', model 'Model Z', and year 2023
tesla = Car("Tesla", "Model Z", 2023)
# Output: Tesla Model Z created

Through the __init__ code, every time a Car object is created, the brand, model, and year of the car are set, and the brand and model are printed.


Defining the End with a Destructor​

A destructor is a method that is called when an object is destroyed.

In Python, it is defined using __del__ and is commonly used to perform clean-up tasks when an object is deleted.

Defining a Destructor
class Car:
    # Define the destructor
    def __del__(self):
        # Print when the object is destroyed
        print(f"{self.brand} {self.model} is being destroyed")

Defining Behavior with Methods​

A method defines the behavior an object can perform.

Methods typically change the object's state or perform a specific action.

Defining Methods
class Car:
    def __init__(self, brand, model, year):
        self.brand = brand
        self.model = model
        self.year = year

    def start_engine(self):
        print(f"Starting the engine of {self.brand} {self.model}")

    def change_year(self, year):
        self.year = year
        print(f"The year of {self.brand} {self.model} has been changed to {year}")

# Create a car object with brand 'Lamboo', model 'Avent', and year 2021
lambo = Car("Lamboo", "Avent", 2021)

# Output: Starting the engine of Lamboo Avent
lambo.start_engine()

# Output: The year of Lamboo Avent has been changed to 2023
lambo.change_year(2023)

In the code above, the start_engine method expresses the action of starting the car's engine, and the change_year method changes the car's year.

The self keyword included when defining methods refers to the instance of the object calling the method and must be included when defining methods.

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