OOP principles overview in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a class named Car.

Python

class [1]:
    pass

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

Acar

BCar

Cvehicle

DAuto

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase names for classes.

Using unrelated names.

The class name should be Car with a capital C to follow Python naming conventions.

2fill in blank

medium

Complete the code to create an object my_car from the Car class.

Python

my_car = [1]()

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

Acar

BAuto

Cvehicle

DCar

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase class names when creating objects.

Forgetting parentheses after the class name.

To create an object, call the class name Car followed by parentheses.

3fill in blank

hard

Fix the error in the method definition to correctly define the constructor.

Python

class Car:
    def [1](self, make):
        self.make = make

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

A__init__

Binit

Cconstructor

Dinitialize

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'init' without underscores.

Using other names like 'constructor' or 'initialize'.

The constructor method in Python is named __init__ with double underscores before and after.

4fill in blank

hard

Fill both blanks to define a method display_make that prints the car's make.

Python

class Car:
    def __init__(self, make):
        self.make = make
    def [1](self):
        print(self.[2])

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

Adisplay_make

Bmake

Cmodel

Dshow_make

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong method names.

Printing an attribute that does not exist.

The method name should be display_make and it should print the make attribute.

5fill in blank

hard

Fill all three blanks to create a subclass ElectricCar that inherits from Car and adds a battery_size attribute.

Python

class [1]([2]):
    def __init__(self, make, battery_size):
        super().[3](make)
        self.battery_size = battery_size

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

AElectricCar

BCar

C__init__

DBatteryCar

Attempts:

3 left

💡 Hint

Common Mistakes

Not calling the parent constructor properly.

Using wrong class or method names.

The subclass is named ElectricCar, inherits from Car, and calls the parent's constructor using super().__init__(make).

Practice

1. Which of the following is NOT one of the four main principles of Object-Oriented Programming (OOP)?

easy

A. Compilation

B. Inheritance

C. Polymorphism

D. Encapsulation

Solution

1. Step 1: Recall the four main OOP principles

   The four main principles are Encapsulation, Inheritance, Polymorphism, and Abstraction.

2. Step 2: Identify the option not in the list

   Compilation is a process related to converting code, not an OOP principle.

3. Final Answer:

   Compilation -> Option A

4. Quick Check:

   OOP principles exclude Compilation [OK]

Hint: Remember OOP principles: E, I, P, A [OK]

Common Mistakes:

• Confusing compilation with OOP concepts
• Mixing up abstraction with compilation
• Thinking all programming terms are OOP principles

2. Which Python keyword is used to create a new class?

easy

A. def

B. func

C. object

D. class

Solution

1. Step 1: Recall Python syntax for defining classes

   In Python, the keyword class is used to define a new class.

2. Step 2: Check other options

   def defines functions, object is a base class, and func is not a Python keyword.

3. Final Answer:

   class -> Option D

4. Quick Check:

   Use 'class' to define classes [OK]

Hint: Classes start with 'class' keyword in Python [OK]

Common Mistakes:

• Using def instead of class for classes
• Confusing object with class keyword
• Trying to use func which is invalid

3. What will be the output of this code?

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

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

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

medium

A. Bark

B. Sound

C. None

D. Error

Solution

1. Step 1: Understand inheritance and method overriding

   Dog class inherits from Animal and overrides the speak method to return "Bark".

2. Step 2: Check which speak method is called

   pet is an instance of Dog, so pet.speak() calls Dog's speak method, returning "Bark".

3. Final Answer:

   Bark -> Option A

4. Quick Check:

   Overridden method returns 'Bark' [OK]

Hint: Child class method overrides parent method [OK]

Common Mistakes:

• Expecting parent class method output
• Confusing method overriding with overloading
• Thinking print outputs None

4. Find the error in this code snippet:

class Car:
    def __init__(self, model):
        self.model = model

    def display(self):
        print(Model)

medium

A. Constructor name is wrong

B. Missing self in display method

C. Model should be self.model in print

D. Class name should be lowercase

Solution

1. Step 1: Check the print statement inside display method

   The print statement uses Model which is undefined; it should use self.model to access the instance variable.

2. Step 2: Verify other parts

   The constructor name __init__ is correct, and method has self parameter. Class name capitalization is fine.

3. Final Answer:

   Model should be self.model in print -> Option C

4. Quick Check:

   Use self to access instance variables [OK]

Hint: Use self.variable to access instance data [OK]

Common Mistakes:

• Forgetting self in method parameters
• Using variable name without self prefix
• Thinking constructor name is incorrect

5. You want to create a class that hides its internal data and only allows access through methods. Which OOP principle does this demonstrate?

hard

A. Inheritance

B. Encapsulation

C. Polymorphism

D. Abstraction

Solution

1. Step 1: Understand the principle of hiding data

   Hiding internal data and controlling access through methods is called Encapsulation.

2. Step 2: Differentiate from other principles

   Inheritance is about reusing code, Polymorphism is about using methods in different ways, Abstraction is about hiding complexity but not necessarily data.

3. Final Answer:

   Encapsulation -> Option B

4. Quick Check:

   Data hiding = Encapsulation [OK]

Hint: Data hiding means Encapsulation [OK]

Common Mistakes:

• Confusing encapsulation with abstraction
• Mixing inheritance with data hiding
• Thinking polymorphism hides data