OOP principles overview in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this code using inheritance?

Consider this Python code that uses inheritance. What will it print when run?

Python

class Animal:
    def sound(self):
        return "Some sound"

class Dog(Animal):
    def sound(self):
        return "Bark"

pet = Dog()
print(pet.sound())

A TypeError

B Some sound

C None

D Bark

💡 Hint

Think about which method is called when the child class overrides a method from the parent.

The Dog class overrides the sound method from Animal. So calling pet.sound() uses Dog's version, printing Bark.

❓ Predict Output

intermediate

What does this code print demonstrating encapsulation?

Look at this Python class using encapsulation. What will be printed?

Python

class BankAccount:
    def __init__(self, balance):
        self.__balance = balance
    def get_balance(self):
        return self.__balance

account = BankAccount(100)
print(account.__balance)

A None

B 100

C AttributeError

D 0

💡 Hint

Check how private variables are accessed outside the class.

The variable __balance is private and cannot be accessed directly outside the class, causing AttributeError.

🧠 Conceptual

advanced

Which principle does this code best demonstrate?

This code shows a class with a method that behaves differently depending on the object. Which OOP principle is this?

Python

class Shape:
    def area(self):
        return 0

class Square(Shape):
    def __init__(self, side):
        self.side = side
    def area(self):
        return self.side * self.side

class Circle(Shape):
    def __init__(self, radius):
        self.radius = radius
    def area(self):
        return 3.14 * self.radius * self.radius

A Polymorphism

B Inheritance

C Encapsulation

D Abstraction

💡 Hint

Think about how the same method name works differently for different classes.

Polymorphism allows methods with the same name to behave differently depending on the object calling them.

❓ Predict Output

advanced

What is the output of this code demonstrating abstraction?

What will this code print when run?

Python

from abc import ABC, abstractmethod

class Vehicle(ABC):
    @abstractmethod
    def start(self):
        pass

class Car(Vehicle):
    def start(self):
        return "Car started"

my_car = Car()
print(my_car.start())

A Car started

B TypeError

C AttributeError

D Vehicle started

💡 Hint

Look at how abstract methods are implemented in child classes.

The abstract method start is implemented in Car, so calling my_car.start() returns Car started.

❓ Predict Output

expert

What is the value of x after running this code with multiple inheritance?

Consider this code with multiple inheritance. What is the value of x after execution?

Python

class A:
    def __init__(self):
        self.x = 1

class B(A):
    def __init__(self):
        super().__init__()
        self.x = 2

class C(A):
    def __init__(self):
        super().__init__()
        self.x = 3

class D(B, C):
    def __init__(self):
        super().__init__()

obj = D()
x = obj.x

A 1

B 2

C 3

D TypeError

💡 Hint

Check the method resolution order (MRO) for class D.

Class D inherits from B then C. super().__init__() in D calls B's __init__, which sets x=2. So x is 2.