Inheriting attributes and methods in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of inherited method call

What is the output of this Python code that uses inheritance?

Python

class Animal:
    def speak(self):
        return "I make a sound"

class Dog(Animal):
    pass

pet = Dog()
print(pet.speak())

A AttributeError

B "Dog barks"

C "I am an animal"

D "I make a sound"

💡 Hint

The Dog class does not override the speak method.

Since Dog inherits from Animal and does not override speak, calling speak on Dog instance uses Animal's speak method, returning "I make a sound".

❓ Predict Output

intermediate

Value of inherited attribute after modification

What is the value of pet.color after running this code?

Python

class Animal:
    def __init__(self):
        self.color = "brown"

class Dog(Animal):
    def __init__(self):
        super().__init__()
        self.color = "black"

pet = Dog()

A "black"

B "brown"

C None

D AttributeError

💡 Hint

The Dog class calls super().__init__() then changes color.

Dog's __init__ calls Animal's __init__ setting color to "brown", then immediately sets color to "black". So pet.color is "black".

🔧 Debug

advanced

Identify the error in method overriding

What error does this code raise when executed?

Python

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

class Dog(Animal):
    def speak():
        return "bark"

pet = Dog()
print(pet.speak())

A "bark"

B AttributeError: 'Dog' object has no attribute 'speak'

C TypeError: speak() missing 1 required positional argument: 'self'

D SyntaxError

💡 Hint

Check the method signature of speak in Dog.

Dog's speak method lacks the self parameter, so calling pet.speak() passes self implicitly but method expects none, causing TypeError.

❓ Predict Output

advanced

Output of method overriding with super()

What is printed when this code runs?

Python

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

class Dog(Animal):
    def speak(self):
        return super().speak() + " and bark"

pet = Dog()
print(pet.speak())

A "bark"

B "sound and bark"

C "sound"

D AttributeError

💡 Hint

super() calls the parent class method.

Dog's speak calls Animal's speak via super(), which returns "sound", then adds " and bark". So output is "sound and bark".

🧠 Conceptual

expert

Number of attributes in instance after inheritance and modification

Given the code below, how many attributes does the instance 'pet' have?

Python

class Animal:
    def __init__(self):
        self.legs = 4
        self.color = "brown"

class Dog(Animal):
    def __init__(self):
        super().__init__()
        self.color = "black"
        self.tail = True

pet = Dog()

A 3

B 2

C 4

D 1

💡 Hint

Count all attributes set on pet after Dog.__init__ runs.

pet has legs (from Animal), color (overwritten in Dog), and tail (added in Dog), total 3 attributes.

Practice

1. What does it mean when a child class inherits from a parent class in Python?

easy

A. The child class must redefine all methods of the parent class to use them.

B. The child class can only use methods but not attributes of the parent class.

C. The child class automatically has all attributes and methods of the parent class.

D. The child class cannot add any new methods or attributes.

Solution

1. Step 1: Understand inheritance basics

   Inheritance means the child class gets all features (attributes and methods) of the parent class automatically.

2. Step 2: Analyze each option

   The child class automatically has all attributes and methods of the parent class. correctly states this. Options B, C, and D are incorrect because they limit or deny inheritance features.

3. Final Answer:

   The child class automatically has all attributes and methods of the parent class. -> Option C

4. Quick Check:

   Inheritance = automatic access to parent features [OK]

Hint: Inheritance means child gets all parent features automatically [OK]

Common Mistakes:

• Thinking child must redefine parent methods
• Believing child cannot add new features
• Assuming attributes are not inherited

2. Which of the following is the correct syntax to make class Dog inherit from class Animal in Python?

easy

A. class Dog(Animal):

B. class Dog -> Animal:

C. class Dog inherits Animal:

D. class Dog : Animal

Solution

1. Step 1: Recall Python inheritance syntax

   In Python, inheritance is shown by putting the parent class name in parentheses after the child class name.

2. Step 2: Match syntax to options

   class Dog(Animal): uses class Dog(Animal): which is correct. Others use invalid syntax.

3. Final Answer:

   class Dog(Animal): -> Option A

4. Quick Check:

   Inheritance syntax = class Child(Parent): [OK]

Hint: Use parentheses with parent class name after child class [OK]

Common Mistakes:

• Using 'inherits' keyword instead of parentheses
• Using arrow or colon incorrectly
• Omitting parentheses

3. What will be the output of this code?

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

class Child(Parent):
    pass

c = Child()
print(c.greet())

medium

A. Hello from Child

B. Hello from Parent

C. AttributeError

D. SyntaxError

Solution

1. Step 1: Understand method inheritance

   Child class inherits greet method from Parent because it has no own greet.

2. Step 2: Trace the method call

   Calling c.greet() runs Parent's greet returning "Hello from Parent".

3. Final Answer:

   Hello from Parent -> Option B

4. Quick Check:

   Inherited method runs if child has none [OK]

Hint: Child uses parent's method if not overridden [OK]

Common Mistakes:

• Expecting child's own greet method when none exists
• Confusing AttributeError with missing method
• Thinking syntax error occurs

4. Find the error in this code:

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

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

d = Dog()
print(d.sound())

medium

A. print statement syntax error

B. Dog class should not inherit Animal

C. Cannot override methods in child class

D. Missing self parameter in Dog's sound method

Solution

1. Step 1: Check method definitions

   In Python, instance methods must have self as first parameter.

2. Step 2: Identify error in Dog's sound

   Dog's sound method lacks self, causing a TypeError when called on instance.

3. Final Answer:

   Missing self parameter in Dog's sound method -> Option D

4. Quick Check:

   Instance methods need self parameter [OK]

Hint: Always include self as first method parameter [OK]

Common Mistakes:

• Forgetting self in child method
• Thinking inheritance disallows overriding
• Assuming print syntax is wrong

5. Given these classes:

class Vehicle:
    def __init__(self, brand):
        self.brand = brand
    def info(self):
        return f"Vehicle brand: {self.brand}"

class Car(Vehicle):
    def __init__(self, brand, model):
        super().__init__(brand)
        self.model = model
    def info(self):
        return f"Car brand: {self.brand}, model: {self.model}"

What will print(Car('Toyota', 'Corolla').info()) output?

hard

A. Car brand: Toyota, model: Corolla

B. Vehicle brand: Toyota

C. Car brand: , model: Corolla

D. TypeError due to missing argument

Solution

1. Step 1: Understand constructor chaining

   Car's __init__ calls super().__init__(brand) to set brand in Vehicle.

2. Step 2: Analyze info method override

   Car overrides info to include both brand and model.

3. Step 3: Predict output

   Calling info() on Car instance returns "Car brand: Toyota, model: Corolla".

4. Final Answer:

   Car brand: Toyota, model: Corolla -> Option A

5. Quick Check:

   Child overrides method and calls parent's init [OK]

Hint: Use super() to inherit parent init, override methods as needed [OK]

Common Mistakes:

• Forgetting super() call in child __init__
• Expecting parent info output instead of child's
• Confusing missing arguments error