Practice Exercises & Placement Q&A
Test your Object-Oriented Programming mastery with these practical exercises and commonly asked technical interview questions!
Part 1: Practice Exercises 💻​
1. School System Inheritance​
Create a base class Person with name and age attributes. Inherit a child class Teacher that adds a subject attribute and has a method get_details() to print complete teacher info.
2. Encapsulated Car Speed​
Create a class Car with a private attribute __speed initialized to 0. Write methods accelerate(amount) and brake(amount) with validation rules ensuring speed never drops below 0 or exceeds 200. Add a getter get_speed().
3. Custom Shopping Cart with Dunder Methods​
Create a ShoppingCart class that holds a list of items. Implement __len__() to return item count and __str__() to print a summary of the cart.
Part 2: Placement & Technical Interview Q&A 🎯​
Q1. What is the fundamental difference between a Class and an Object?​
Answer: A Class is a conceptual design template or blueprint that defines the variables (attributes) and functions (methods) common to all entities of that type. An Object (Instance) is a physical entity created from that class blueprint that resides in memory and holds actual data.
Q2. Explain the difference between Inheritance and Polymorphism.​
Answer: Inheritance lets a child class inherit properties and behaviors from a parent class, promoting code reusability. Polymorphism allows different classes to share the same method signature while executing distinct implementations (often via method overriding).
Q3. How do you implement private variables in Python, and what is Name Mangling?​
Answer: By prefixing an attribute name with double underscores (__) inside a class (e.g., self.__balance). Python applies Name Mangling behind the scenes, changing the variable name internally to _ClassName__variableName. This prevents external code from directly accessing or modifying the variable.
Q4. What is the difference between __str__ and __repr__?​
Answer: __str__() is intended for end-users and returns a clean, human-readable description when print() is called. __repr__() is intended for developers and returns an unambiguous, technical representation useful for debugging and logging.
Q5. Can you instantiate an Abstract Class directly?​
Answer: No. An abstract base class (inheriting from abc.ABC and containing @abstractmethod) serves strictly as an enforced contract or template. Attempting to instantiate it raises a TypeError. You must inherit it into a child class and implement all abstract methods before instantiating.