Top 5 Python Interview Problems on Classes and Objects

Chapter 4: Build an Employee Management System with Inheritance

🧠 Objective

To explore:

• Inheritance in Python classes
• How to use super() to extend and reuse code
• Overriding methods from a parent class
• Combining shared and specialized behaviors

This is a staple interview topic for testing your ability to design scalable and extensible object hierarchies.

📌 Problem Statement

Create a simple Employee Management System using OOP in Python:

1. Build a base class Employee with common attributes: name, salary
2. Add a method display() to show details
3. Create two subclasses:
• Manager (with additional attribute: department)
• Developer (with additional attribute: programming_language)
4. Override the display() method in each subclass to show additional info
5. Track the total number of employees created using a class variable

🔧 Step-by-Step Implementation

✅ Step 1: Define the Base Class Employee

class Employee:

    total_employees = 0

    def __init__(self, name, salary):

        self.name = name

        self.salary = salary

        Employee.total_employees += 1

    def display(self):

        return f"Name: {self.name}, Salary: ${self.salary}"

✅ Step 2: Create the Manager Subclass

class Manager(Employee):

    def __init__(self, name, salary, department):

        super().__init__(name, salary)

        self.department = department

    def display(self):

        base_info = super().display()

        return f"{base_info}, Department: {self.department}"

✅ Step 3: Create the Developer Subclass

class Developer(Employee):

    def __init__(self, name, salary, programming_language):

        super().__init__(name, salary)

        self.programming_language = programming_language

    def display(self):

        base_info = super().display()

        return f"{base_info}, Language: {self.programming_language}"

🧪 Example Usage

emp1 = Manager("Alice", 90000, "Marketing")

emp2 = Developer("Bob", 85000, "Python")

emp3 = Developer("Charlie", 80000, "JavaScript")

print(emp1.display())

print(emp2.display())

print(emp3.display())

print("Total employees:", Employee.total_employees)

✅ Output:

Name: Alice, Salary: $90000, Department: Marketing

Name: Bob, Salary: $85000, Language: Python

Name: Charlie, Salary: $80000, Language: JavaScript

Total employees: 3

🧠 Class Hierarchy Diagram

             Employee

            /       \

        Manager   Developer

✅ Both Manager and Developer inherit common properties from Employee
✅ Override display() method for specialization

✅ Inheritance vs Composition

✅ Advanced Bonus: Use isinstance()

print(isinstance(emp1, Employee))   # True

print(isinstance(emp1, Developer)) # False

✅ Checks the type hierarchy and inheritance chain.

✅ Summary Table