Question

What is an instance attribute?

Short answer

Answer: Instance attributes are variables associated with specific objects or instances of a class in object-oriented programming languages. These variables store data that may vary from one instance to another, giving each instance its distinct values. Compared to class attributes, which are shared by all instances of a class and belong to the class itself, instance attributes belong to specific instances. Instance attributes are defined within instance methods, while class attributes are defined outside instance methods.

Step-by-step solution

Definition of Instance Attribute

An instance attribute is a variable associated with a specific object or instance of a class in an object-oriented programming (OOP) language. These variables store data that may vary from one instance to another, allowing each instance of the class to have its values.

Instance Attributes vs. Class Attributes

In contrast to instance attributes, class attributes are shared by all instances of a class. While instance attributes belong to specific instances, class attributes belong to the class itself. An easy way to distinguish them is to remember that instance attributes are defined within instance methods (i.e., the methods that require an instance of the class), whereas class attributes are defined outside instance methods.

Example of Instance Attributes

Let's take a look at an example to better understand the concept of instance attributes. Consider a simple class `Dog`: ```python class Dog: # Class attribute species = "Canis familiaris" # Instance attributes (defined in the __init__ method) def __init__(self, name, age): self.name = name self.age = age ``` In this example, the `Dog` class has one class attribute `species` and two instance attributes: `name` and `age`. The instance attributes `name` and `age` are defined within the `__init__` method, which is executed when a new instance of the class is created. ```python # Create two Dog instances dog1 = Dog("Max", 3) dog2 = Dog("Buddy", 5) # Accessing and comparing their instance attributes print(dog1.name) # Output: Max print(dog2.name) # Output: Buddy print(dog1.age) # Output: 3 print(dog2.age) # Output: 5 # Comparing their class attribute print(dog1.species) # Output: Canis familiaris print(dog2.species) # Output: Canis familiaris ``` As you can see, `dog1` and `dog2` are two different instances of the `Dog` class and have different values for their instance attributes `name` and `age`. However, they share the same class attribute `species`.