Method overriding in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of method overriding in inheritance

What is the output of this Python code that uses method overriding?

Python

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

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

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

A "Bark"

B "Some sound"

C None

D TypeError

💡 Hint

Look at which class's method is called when you create a Dog object.

The Dog class overrides the sound method of Animal. So calling sound on a Dog instance returns "Bark".

❓ Predict Output

intermediate

Output when calling overridden method with super()

What will this code print when calling the speak method?

Python

class Parent:
    def speak(self):
        return "Hello from Parent"

class Child(Parent):
    def speak(self):
        return super().speak() + " and Child"

obj = Child()
print(obj.speak())

A "Hello from Parent"

B AttributeError

C "and Child"

D "Hello from Parent and Child"

💡 Hint

super() calls the method from the parent class.

The Child's speak method calls the Parent's speak using super(), then adds " and Child".

❓ Predict Output

advanced

Output of multiple inheritance with method overriding

What is the output of this code using multiple inheritance and method overriding?

Python

class A:
    def greet(self):
        return "Hello from A"

class B(A):
    def greet(self):
        return "Hello from B"

class C(A):
    def greet(self):
        return "Hello from C"

class D(B, C):
    pass

obj = D()
print(obj.greet())

A "Hello from B"

B TypeError

C "Hello from C"

D "Hello from A"

💡 Hint

Python uses the method resolution order (MRO) to decide which method to call.

Class D inherits from B and C. B's greet overrides A's. D uses B's greet because B is before C in inheritance.

❓ Predict Output

advanced

Output when overriding method with different parameters

What will this code print?

Python

class Base:
    def info(self):
        return "Base info"

class Derived(Base):
    def info(self, detail):
        return f"Derived info: {detail}"

obj = Derived()
print(obj.info())

A "Base info"

B "Derived info: None"

C TypeError

D AttributeError

💡 Hint

Check if the method call matches the method signature in Derived.

Derived's info requires one argument, but obj.info() is called without arguments, causing TypeError.

🧠 Conceptual

expert

Understanding method overriding behavior with super() and multiple inheritance

Given the following classes, what is the output of calling obj.action()?

Python

class X:
    def action(self):
        return "X"

class Y(X):
    def action(self):
        return "Y" + super().action()

class Z(X):
    def action(self):
        return "Z" + super().action()

class W(Y, Z):
    def action(self):
        return "W" + super().action()

obj = W()
print(obj.action())

A "WZYX"

B "WYZX"

C "WXYZ"

D "WXYZX"

💡 Hint

Check the method resolution order (MRO) for class W and how super() calls chain.

The MRO for W is W -> Y -> Z -> X. Each action calls super().action(), so the output concatenates in order: W + Y + Z + X = "WYZX".

Practice

1.

What is method overriding in Python?

Choose the best description.

easy

A. A child class provides a new version of a method from its parent class.

B. A method that is called automatically when an object is created.

C. A method that cannot be changed once defined in a class.

D. A method that is only accessible inside the class it is defined.

Solution

1. Step 1: Understand method overriding concept

   Method overriding means a child class changes a method from its parent by defining a method with the same name.

2. Step 2: Match description to concept

   A child class provides a new version of a method from its parent class. correctly describes this behavior, while others describe different concepts.

3. Final Answer:

   A child class provides a new version of a method from its parent class. -> Option A

4. Quick Check:

   Method overriding = child changes parent method [OK]

Hint: Child class method with same name replaces parent method [OK]

Common Mistakes:

• Confusing overriding with overloading
• Thinking overriding means creating a new method
• Believing methods cannot be changed in child classes

2.

Which of the following is the correct way to override a method greet in a child class?

class Parent:
    def greet(self):
        print("Hello from Parent")

class Child(Parent):
    # What goes here?

easy

A. def greet():
print("Hello from Child")

B. def greet(self):
print("Hello from Child")

C. def greet(self, name):
print(f"Hello {name} from Child")

D. def greet(self):
return "Hello from Child"

Solution

1. Step 1: Check method signature for overriding

   The child method must have the same name and parameters as the parent method to override it properly.

2. Step 2: Compare options

   def greet(self): print("Hello from Child") matches the parent's method signature exactly. def greet(): print("Hello from Child") misses 'self', C adds a parameter, and D returns a string instead of printing.

3. Final Answer:

   def greet(self):\n print("Hello from Child") -> Option B

4. Quick Check:

   Same method name and parameters = correct override [OK]

Hint: Match method name and parameters exactly to override [OK]

Common Mistakes:

• Omitting 'self' parameter in method
• Changing method parameters when overriding
• Returning value instead of matching parent's behavior

3.

What will be the output of the following code?

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

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

pet = Dog()
pet.sound()

medium

A. Some sound

B. None

C. Error: Method not found

D. Bark

Solution

1. Step 1: Identify method overriding in Dog class

   Dog class overrides the sound() method from Animal to print "Bark" instead of "Some sound".

2. Step 2: Check which method is called

   When pet.sound() is called, it uses Dog's version, printing "Bark".

3. Final Answer:

   Bark -> Option D

4. Quick Check:

   Child method called = overridden output [OK]

Hint: Child method replaces parent method output [OK]

Common Mistakes:

• Expecting parent method output instead of child's
• Thinking method call causes error
• Confusing print output with return value

4.

Find the error in this code that tries to override a method:

class Vehicle:
    def start(self):
        print("Vehicle started")

class Car(Vehicle):
    def start():
        print("Car started")

c = Car()
c.start()

medium

A. Missing 'self' parameter in Car's start method

B. Car class should not inherit Vehicle

C. Parent method start() is private and cannot be overridden

D. Calling start() without parentheses

Solution

1. Step 1: Check method signature in child class

   Car's start method is missing the 'self' parameter, which is required for instance methods.

2. Step 2: Understand impact of missing 'self'

   Without 'self', Python treats start as a static method, causing a TypeError when called on an instance.

3. Final Answer:

   Missing 'self' parameter in Car's start method -> Option A

4. Quick Check:

   Instance methods need 'self' parameter [OK]

Hint: Always include 'self' as first parameter in instance methods [OK]

Common Mistakes:

• Forgetting 'self' in child method
• Thinking inheritance causes error
• Misunderstanding method call syntax

5.

Given the classes below, what will be the output when c.describe() is called?

class Parent:
    def describe(self):
        print("Parent description")

class Child(Parent):
    def describe(self):
        print("Child description")
        super().describe()

c = Child()
c.describe()

hard

A. Child description

B. Parent description\nChild description

C. Child description\nParent description

D. Error: super() used incorrectly

Solution

1. Step 1: Understand method overriding with super()

   Child's describe() overrides Parent's but calls super().describe() to run parent's method too.

2. Step 2: Trace method calls

   Calling c.describe() prints "Child description" first, then calls Parent's describe() printing "Parent description".

3. Final Answer:

   Child description\nParent description -> Option C

4. Quick Check:

   super() calls parent method after child override [OK]

Hint: super() calls parent method inside child override [OK]

Common Mistakes:

• Expecting only child's print output
• Thinking super() causes error
• Confusing order of prints