Extending parent behavior in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of extended method with super() call

What is the output of this Python code when calling Child().greet()?

Python

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

class Child(Parent):
    def greet(self):
        parent_msg = super().greet()
        return parent_msg + " and Child"  

print(Child().greet())

A "Hello from Parent and Child"

B "Hello from Child"

C "Hello from Parent"

D TypeError

💡 Hint

Think about how super() calls the parent method and how the strings are combined.

The Child class calls super().greet() which returns "Hello from Parent". Then it adds " and Child" to that string, so the final output is "Hello from Parent and Child".

❓ Predict Output

intermediate

Output when parent method is not called

What will be printed when running this code?

Python

class Parent:
    def action(self):
        print("Parent action")

class Child(Parent):
    def action(self):
        print("Child action")

obj = Child()
obj.action()

A Child action

B Parent action

C Parent action\nChild action

D AttributeError

💡 Hint

Check which method is called when the child overrides the parent method without calling super().

The Child class overrides the action method and does not call super(). So only "Child action" is printed.

🔧 Debug

advanced

Why does this code raise an error?

This code tries to extend the parent method but raises an error. What is the cause?

Python

class Parent:
    def calculate(self, x):
        return x * 2

class Child(Parent):
    def calculate(self, x):
        return super().calculate(x) + 3

print(Child().calculate(4))

A SyntaxError due to missing colon

B Missing return statement in Child.calculate

C Parent.calculate requires two arguments

D super is used without parentheses, causing AttributeError

💡 Hint

Check how super() is called in Python 3.

In Python 3, super() must be called with parentheses to get the super object. Using super.calculate(x) causes an AttributeError because super is a built-in function, not an object.

❓ Predict Output

advanced

Output of multiple inheritance with super()

What is the output of this code?

Python

class A:
    def process(self):
        return "A"

class B(A):
    def process(self):
        return super().process() + "B"

class C(A):
    def process(self):
        return super().process() + "C"

class D(B, C):
    def process(self):
        return super().process() + "D"

print(D().process())

A "ABDC"

B "ABCD"

C "ACBD"

D "AB"

💡 Hint

Remember Python uses Method Resolution Order (MRO) in multiple inheritance.

The MRO for class D is D -> B -> C -> A. Each super().process() calls the next in line: D calls B, B calls C, C calls A, resulting in "A" (A) + "C" (C) + "B" (B) + "D" (D) = "ACBD".

🧠 Conceptual

expert

Why use super() in method overriding?

Which of the following best explains why we use super() when overriding a method in a child class?

A To prevent the child class method from running

B To call the parent class method and extend its behavior without rewriting it

C To create a new method unrelated to the parent class

D To call a method from a sibling class

💡 Hint

Think about how inheritance helps reuse code.

Using super() allows the child class to run the parent class method, then add or change behavior, so we don't have to rewrite the parent's code.

Practice

1. What does super() do in a child class method?

easy

A. It overrides the child class method completely.

B. It calls the parent class method to reuse its behavior.

C. It deletes the parent class method.

D. It creates a new instance of the child class.

Solution

1. Step 1: Understand the role of super()

   super() is used to call a method from the parent class inside a child class method.

2. Step 2: Recognize code reuse

   By calling the parent method, the child can reuse existing behavior and add new features without rewriting code.

3. Final Answer:

   It calls the parent class method to reuse its behavior. -> Option B

4. Quick Check:

   super() calls parent method = D [OK]

Hint: Remember: super() runs parent method inside child [OK]

Common Mistakes:

• Thinking super() creates new instances
• Believing super() deletes methods
• Assuming super() overrides without calling parent

2. Which of the following is the correct syntax to call a parent class method greet inside a child class method in Python?

easy

A. super().greet()

B. super.greet()

C. parent.greet()

D. self.super.greet()

Solution

1. Step 1: Recall correct super() syntax

   In Python, super() is a function and must be called with parentheses before accessing methods.

2. Step 2: Identify correct method call

   The correct way to call the parent method is super().greet(), not super.greet() or others.

3. Final Answer:

   super().greet() -> Option A

4. Quick Check:

   super() needs parentheses = A [OK]

Hint: Use parentheses with super() to call parent methods [OK]

Common Mistakes:

• Omitting parentheses after super
• Using parent instead of super
• Trying to access super as an attribute

3. What will be the output of this code?

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

class Child(Parent):
    def greet(self):
        super().greet()
        print('Hello from Child')

c = Child()
c.greet()

medium

A. Hello from Child

B. Error: super() not defined

C. Hello from Parent

D. Hello from Parent
Hello from Child

Solution

1. Step 1: Trace the child greet() method

   The child method calls super().greet() first, which prints 'Hello from Parent'.

2. Step 2: Continue child method execution

   After calling the parent method, it prints 'Hello from Child'. So both lines print in order.

3. Final Answer:

   Hello from Parent Hello from Child -> Option D

4. Quick Check:

   super() calls parent then child prints = B [OK]

Hint: super() runs parent code first, then child adds more [OK]

Common Mistakes:

• Ignoring the parent print
• Expecting only child output
• Thinking super() causes error

4. Find the error in this code that tries to extend the parent method:

class Parent:
    def show(self):
        print('Parent show')

class Child(Parent):
    def show(self):
        super.show()
        print('Child show')

medium

A. super.show() should be super().show()

B. Child class must not override show()

C. Parent class method show() is missing self

D. print statements must be inside __init__

Solution

1. Step 1: Check super() usage

   The code uses super.show() which is incorrect syntax; super() must be called as a function.

2. Step 2: Correct the syntax

   It should be super().show() to properly call the parent method.

3. Final Answer:

   super.show() should be super().show() -> Option A

4. Quick Check:

   super() needs parentheses to call methods = A [OK]

Hint: Always use super() with parentheses to call parent methods [OK]

Common Mistakes:

• Forgetting parentheses after super
• Thinking parent method needs no self
• Believing print must be in __init__

5. You want to extend a parent class method calculate so that the child class adds 10 to the parent's result. Which code correctly does this?

class Parent:
    def calculate(self):
        return 5

class Child(Parent):
    def calculate(self):
        # Fill here

hard

A. return Parent.calculate() + 10

B. return calculate() + 10

C. return super().calculate() + 10

D. return self.calculate() + 10

Solution

1. Step 1: Use super() to call parent method

   To get the parent's result, call super().calculate() inside the child method.

2. Step 2: Add 10 to the parent's result

   Return the parent's value plus 10 as super().calculate() + 10.

3. Final Answer:

   return super().calculate() + 10 -> Option C

4. Quick Check:

   super() calls parent, add 10 = C [OK]

Hint: Use return super().method() + extra to extend result [OK]

Common Mistakes:

• Calling calculate() without super causes recursion
• Calling Parent.calculate() without instance
• Using self.calculate() causes infinite loop