Polymorphism through inheritance in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a method that prints a greeting.

Python

class Animal:
    def speak(self):
        print([1])

pet = Animal()
pet.speak()

Drag options to blanks, or click blank then click option'

AHello

B"Hello!"

Cprint("Hello!")

Dreturn "Hello!"

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around the string.

Using return instead of print.

Trying to print inside the print statement.

The speak method should print the string Hello!. Using quotes around the string is necessary.

2fill in blank

medium

Complete the code to override the speak method in the Dog class.

Python

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

class Dog(Animal):
    def speak(self):
        print([1])

pet = Dog()
pet.speak()

Drag options to blanks, or click blank then click option'

Areturn "Woof!"

BWoof!

Cprint("Woof!")

D"Woof!"

Attempts:

3 left

💡 Hint

Common Mistakes

Not using quotes around the string.

Using print inside print.

Using return instead of print.

The Dog class overrides speak to print "Woof!". The string must be quoted.

3fill in blank

hard

Fix the error in the code to call the speak method of the Cat class.

Python

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

class Cat(Animal):
    def speak(self):
        print("Meow!")

pet = Cat()
pet.[1]()

Drag options to blanks, or click blank then click option'

Aspeak

Bsay

Csound

Dtalk

Attempts:

3 left

💡 Hint

Common Mistakes

Using method names not defined in the class.

Forgetting parentheses when calling the method.

The method to call is speak. Other names do not exist and cause errors.

4fill in blank

hard

Fill both blanks to create a list of animals and call their speak methods.

Python

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

class Bird(Animal):
    def speak(self):
        print("Chirp!")

animals = [[1], [2]]
for pet in animals:
    pet.speak()

Drag options to blanks, or click blank then click option'

AAnimal()

BBird()

CDog()

DCat()

Attempts:

3 left

💡 Hint

Common Mistakes

Using class names without parentheses.

Using classes not defined in the code.

The list animals contains an Animal and a Bird instance. Both have a speak method.

5fill in blank

hard

Fill both blanks to create a dictionary mapping animal names to their sounds using polymorphism.

Python

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

class Dog(Animal):
    def speak(self):
        return "Woof!"

class Cat(Animal):
    def speak(self):
        return "Meow!"

pets = [Dog(), Cat()]
sounds = { = {pet.{BLANK_2}}(): pet.{{BLANK_2}}() for pet in pets}

Drag options to blanks, or click blank then click option'

A{

Bspeak

D[

Attempts:

3 left

💡 Hint

Common Mistakes

Using square brackets instead of curly braces for dictionary.

Not calling the method with parentheses.

Using different method names.

The dictionary is created with curly braces {}. The keys and values come from calling speak() on each pet.

Practice

1. What does polymorphism through inheritance allow in Python?

easy

A. One method name to have different behaviors in child classes

B. Multiple inheritance from unrelated classes

C. Using the same variable name in different functions

D. Creating objects without defining classes

Solution

1. Step 1: Understand polymorphism concept

   Polymorphism means one method name can behave differently depending on the class.

2. Step 2: Relate to inheritance

   Child classes override the method to provide their own behavior.

3. Final Answer:

   One method name to have different behaviors in child classes -> Option A

4. Quick Check:

   Polymorphism = One method, many behaviors [OK]

Hint: Polymorphism means same method, different actions [OK]

Common Mistakes:

• Confusing polymorphism with multiple inheritance
• Thinking polymorphism means same variable names
• Believing objects can exist without classes

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

easy

A. Call the parent method inside the child method without redefining

B. Use the keyword override before the method

C. Define a method with the same name in the child class

D. Rename the method in the child class

Solution

1. Step 1: Check method overriding syntax

   In Python, overriding means defining a method with the same name in the child class.

2. Step 2: Verify other options

   Python does not use override keyword; renaming is not overriding; calling parent method alone is not overriding.

3. Final Answer:

   Define a method with the same name in the child class -> Option C

4. Quick Check:

   Override = same method name in child [OK]

Hint: Override by redefining method name in child class [OK]

Common Mistakes:

• Using a non-existent override keyword
• Thinking calling parent method equals overriding
• Renaming method instead of overriding

3. What will be the output of this code?

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

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

class Cat(Animal):
    def sound(self):
        return "Meow"

animals = [Dog(), Cat(), Animal()]
for a in animals:
    print(a.sound())

medium

A. Bark\nMeow\nSome sound

B. Some sound\nSome sound\nSome sound

C. Bark\nMeow\nError

D. Error\nError\nError

Solution

1. Step 1: Identify method overriding

   Dog and Cat classes override sound method to return "Bark" and "Meow" respectively.

2. Step 2: Trace the loop output

   Loop calls sound() on Dog(), Cat(), and Animal() objects, printing "Bark", "Meow", and "Some sound".

3. Final Answer:

   Bark Meow Some sound -> Option A

4. Quick Check:

   Overridden methods print their own sounds [OK]

Hint: Child method overrides parent, prints child's return [OK]

Common Mistakes:

• Assuming parent method always runs
• Expecting errors from calling base class method
• Mixing output order

4. Find the error in this code that tries to demonstrate polymorphism:

class Vehicle:
    def move(self):
        print("Moving")

class Car(Vehicle):
    def move(self):
        print("Driving")

class Bike(Vehicle):
    def move(self):
        print("Riding")

vehicles = [Car(), Bike()]
for v in vehicles:
    v.move

medium

A. List should include Vehicle() instance

B. Incorrect class inheritance syntax

C. Using print instead of return in methods

D. Missing parentheses when calling move method

Solution

1. Step 1: Check method calls in loop

   The code uses v.move without parentheses, so method is not called.

2. Step 2: Understand effect of missing parentheses

   Without parentheses, method object is referenced but not executed, so no output occurs.

3. Final Answer:

   Missing parentheses when calling move method -> Option D

4. Quick Check:

   Method call needs () to execute [OK]

Hint: Always add () to call methods [OK]

Common Mistakes:

• Forgetting parentheses on method calls
• Thinking print vs return causes error here
• Believing inheritance syntax is wrong

5. You want to add a new class Bird that also uses polymorphism with sound(). Which code correctly extends the existing classes and uses polymorphism?

hard

A. class Bird:
def sound(self):
return "Chirp"

animals.append(Bird())
for a in animals:
print(a.sound())

B. class Bird(Animal):
def sound(self):
return "Chirp"

animals.append(Bird())
for a in animals:
print(a.sound())

C. class Bird(Animal):
def noise(self):
return "Chirp"

animals.append(Bird())
for a in animals:
print(a.sound())

D. class Bird(Animal):
def sound(self):
print("Chirp")

animals.append(Bird())
for a in animals:
print(a.sound())

Solution

1. Step 1: Check inheritance and method name

   Bird must inherit from Animal and override sound() method to maintain polymorphism.

2. Step 2: Verify method behavior and usage

   Method returns string "Chirp" like others; appending Bird() to animals list and calling sound() works correctly.

3. Final Answer:

   Correctly inherits Animal and overrides sound() returning "Chirp" -> Option B

4. Quick Check:

   Polymorphism needs same method name and inheritance [OK]

Hint: Inherit and override same method name with matching signature [OK]

Common Mistakes:

• Not inheriting from Animal class
• Using different method name like noise()
• Printing inside method instead of returning