Instance attributes and methods

Instance attributes are pieces of information specific to each object (or instance) of a class. Think of them as the "personal details" of an object. For example:

• A dog has a name and a breed.
• A car has a color and a brand.

Each object has its own unique set of attributes.

How do you define instance attributes?

You define them inside the __init__ method (the constructor). These attributes are usually set when you create the object. Here’s an example:

class Dog:
    def __init__(self, name, breed):  # Initialize attributes
        self.name = name             # Instance attribute for the name
        self.breed = breed           # Instance attribute for the breed

In this example:

• self.name and self.breed are instance attributes.
• The name and breed values are provided when creating a Dog object.

How to access instance attributes?

You can access instance attributes using the dot . operator:

# Creating an object
my_dog = Dog("Buddy", "Golden Retriever")

# Accessing attributes
print(my_dog.name)   # Output: Buddy
print(my_dog.breed)  # Output: Golden Retriever

Each object (instance) keeps its own information. If you create another dog, it will have its own unique attributes:

another_dog = Dog("Max", "Beagle")
print(another_dog.name)   # Output: Max
print(another_dog.breed)  # Output: Beagle

What are instance methods?

Instance methods are actions that an object can perform. These methods usually work with the instance attributes of the object.

How do you define instance methods?

To define an instance method, you write a function inside the class. The first parameter of the method is always self, which refers to the specific object (or instance) that is calling the method. For example:

class Dog:
    def __init__(self, name, breed):
        self.name = name
        self.breed = breed

    def bark(self):  # Instance method
        return f"{self.name} says Woof!"

Here’s what’s happening:

• bark(self) is an instance method.
• It uses self.name to access the name of the specific dog.

How to use instance methods?

You call an instance method using the dot . operator:

# Creating an object
my_dog = Dog("Buddy", "Golden Retriever")

# Calling the instance method
print(my_dog.bark())  # Output: Buddy says Woof!

If you create another dog, it can use the same method but with its own attributes:

another_dog = Dog("Max", "Beagle")
print(another_dog.bark())  # Output: Max says Woof!

Putting it all together

Here’s a full example with attributes and methods:

class Car:
    def __init__(self, brand, color):
        self.brand = brand  # Instance attribute
        self.color = color  # Instance attribute

    def start(self):  # Instance method
        return f"The {self.color} {self.brand} is starting!"

# Create objects
car1 = Car("Toyota", "red")
car2 = Car("Tesla", "blue")

# Access attributes
print(car1.brand)  # Output: Toyota
print(car2.color)  # Output: blue

# Call methods
print(car1.start())  # Output: The red Toyota is starting!
print(car2.start())  # Output: The blue Tesla is starting!