Method overriding behavior in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of method overriding with super()

What is the output of this Python code?

Python

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

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

obj = Child()
print(obj.greet())

A TypeError

B Hello from Parent

C and Child

D Hello from Parent and Child

💡 Hint

Think about how super() calls the parent method and how the returned string is combined.

The Child class overrides greet but calls the Parent's greet using super(). The returned string from Parent is combined with ' and Child', so the final output is 'Hello from Parent and Child'.

❓ Predict Output

intermediate

Output when overriding without calling super()

What will this code print?

Python

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

class Derived(Base):
    def message(self):
        return "Derived message"

obj = Derived()
print(obj.message())

A AttributeError

B Derived message

C None

D Base message

💡 Hint

The Derived class replaces the Base method without calling it.

Since Derived overrides message and does not call super(), the method from Derived is used, printing 'Derived message'.

❓ Predict Output

advanced

Output with multiple inheritance and method overriding

What is the output of this code?

Python

class A:
    def speak(self):
        return "A speaks"

class B(A):
    def speak(self):
        return "B speaks"

class C(A):
    def speak(self):
        return "C speaks"

class D(B, C):
    pass

obj = D()
print(obj.speak())

A B speaks

B A speaks

C C speaks

D TypeError

💡 Hint

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

Class D inherits from B and C. Python uses MRO and finds speak in B first, so 'B speaks' is printed.

❓ Predict Output

advanced

Output when overriding a method and changing return type

What will this code print?

Python

class Parent:
    def get_value(self):
        return 10

class Child(Parent):
    def get_value(self):
        return "Ten"

obj = Child()
print(obj.get_value())

A Ten

B TypeError

C 10

D AttributeError

💡 Hint

The Child method returns a string instead of an integer.

The Child class overrides get_value and returns the string 'Ten'. Python allows this change in return type, so 'Ten' is printed.

❓ Predict Output

expert

Output with method overriding and attribute access

What is the output of this code?

Python

class Parent:
    def __init__(self):
        self.value = 5
    def get_value(self):
        return self.value

class Child(Parent):
    def __init__(self):
        self.value = 10
    def get_value(self):
        return super().get_value() + 5

obj = Child()
print(obj.get_value())

A 10

B 5

C 15

D AttributeError

💡 Hint

Consider which __init__ method runs and what self.value is when super().get_value() is called.

Child's __init__ does not call Parent's __init__, so Parent's self.value is never set. Child sets self.value to 10. But super().get_value() uses Parent's method which accesses self.value on the Child instance, which is 10. So super().get_value() returns 10, then +5 makes 15. However, since Parent's __init__ is not called, self.value is set by Child to 10. So output is 15.

Practice

1. What does method overriding allow a child class to do in Python?

easy

A. Prevent the parent class method from being used anywhere

B. Create a new method with a different name

C. Change the behavior of a method inherited from the parent class

D. Automatically call the parent class method without code

Solution

1. Step 1: Understand method overriding concept

   Method overriding means the child class provides its own version of a method that exists in the parent class.

2. Step 2: Identify what overriding changes

   The child class method replaces the parent's method behavior when called on the child instance.

3. Final Answer:

   Change the behavior of a method inherited from the parent class -> Option C

4. Quick Check:

   Method overriding = change inherited method behavior [OK]

Hint: Overriding means child changes parent's method behavior [OK]

Common Mistakes:

• Thinking overriding creates a new method with a different name
• Believing overriding disables parent method everywhere
• Assuming parent method is called automatically without super()

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

easy

A. def greet(self, extra):\n print('Hello from child')

B. def greet(self):\n print('Hello from child')

C. def greet_child(self):\n print('Hello from child')

D. def greet():\n print('Hello from child')

Solution

1. Step 1: Match method name exactly

   Overriding requires the child method to have the same name as the parent method, here 'greet'.

2. Step 2: Check method signature

   The method must include 'self' as the first parameter to be a proper instance method.

3. Final Answer:

   def greet(self):\n print('Hello from child') -> Option B

4. Quick Check:

   Same name and self parameter = correct override [OK]

Hint: Override by matching method name and self parameter [OK]

Common Mistakes:

• Changing method name instead of overriding
• Omitting self parameter in method definition
• Adding extra parameters that don't match parent method

3. What will be the output of this code?

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

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

obj = Child()
obj.greet()

medium

A. Hello from Parent

B. Error: greet method not found

C. Hello from Parent\nHello from Child

D. Hello from Child

Solution

1. Step 1: Identify method overriding

   The Child class defines its own greet method, overriding Parent's greet.

2. Step 2: Determine which method is called

   Calling obj.greet() on a Child instance calls the Child's greet method, printing 'Hello from Child'.

3. Final Answer:

   Hello from Child -> Option D

4. Quick Check:

   Child method overrides Parent method = 'Hello from Child' [OK]

Hint: Child method runs when overridden, not parent's [OK]

Common Mistakes:

• Expecting both parent and child messages to print
• Thinking parent method runs instead of child
• Assuming error due to method name conflict

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

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

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

obj = Child()
obj.show()

medium

A. Missing self parameter in Child's show method

B. Parent class method show is private

C. Child class should not override show method

D. obj.show() should be called as Child.show(obj)

Solution

1. Step 1: Check method signature in Child class

   The Child's show method is missing the 'self' parameter, so it is not a proper instance method.

2. Step 2: Understand impact of missing self

   Calling obj.show() will cause a TypeError because Python expects the first argument (self) but none is defined.

3. Final Answer:

   Missing self parameter in Child's show method -> Option A

4. Quick Check:

   Instance methods must have self parameter [OK]

Hint: Instance methods always need self as first parameter [OK]

Common Mistakes:

• Ignoring missing self parameter
• Thinking method overriding is not allowed
• Believing calling method differently fixes error

5. Given this code, what will be the output?

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

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

obj = Child()
obj.greet()

hard

A. Hello from Parent\nHello from Child

B. Hello from Child

C. Hello from Parent

D. Error: super() used incorrectly

Solution

1. Step 1: Understand super() call in Child's greet

   The Child's greet method calls super().greet(), which runs the Parent's greet method first.

2. Step 2: Follow the print statements

   First, 'Hello from Parent' is printed, then 'Hello from Child' is printed after.

3. Final Answer:

   Hello from Parent\nHello from Child -> Option A

4. Quick Check:

   super() calls parent method before child code [OK]

Hint: super() runs parent method before child code [OK]

Common Mistakes:

• Expecting only child's message to print
• Thinking super() causes error without arguments
• Ignoring order of print statements