Real-world modeling using objects 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

BEngine

CDrive

DVehicle

Attempts:

3 left

💡 Hint

Common Mistakes

Using a generic name like Vehicle instead of Car.

The class name should be Car to model a car object.

2fill in blank

medium

Complete the code to add an __init__ method that sets the car's color.

Python

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

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

Amodel

Bspeed

Csize

Dcolor

Attempts:

3 left

💡 Hint

Common Mistakes

Using a parameter name that does not match the attribute name.

The parameter color is needed to set the car's color attribute.

3fill in blank

hard

Fix the error in the method to return the car's color.

Python

class Car:
    def __init__(self, color):
        self.color = color
    def get_color(self):
        return self.[1]

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

Acolor

Bcolour

CColor

Dcol

Attempts:

3 left

💡 Hint

Common Mistakes

Using a misspelled or differently cased attribute name.

The attribute is named color, so the method should return self.color.

4fill in blank

hard

Fill both blanks to create a method that changes the car's color.

Python

class Car:
    def __init__(self, color):
        self.color = color
    def [1](self, [2]):
        self.color = new_color

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

Achange_color

Bcolor

Cnew_color

Dget_color

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method name that does not match the action or a parameter name that doesn't match the assignment.

The method name should be change_color and the parameter new_color to update the color.

5fill in blank

hard

Fill all three blanks to create a Car object and print its color.

Python

my_car = [1]([2])
print(my_car.[3]())

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

ACar

B'red'

Cget_color

Dcolor

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around the color string or calling the attribute directly instead of the method.

Create a Car object with color 'red' and call the get_color() method to print it.

Practice

1. Which of the following best describes an object in Python when modeling real-world things?

easy

A. An object is just a list of numbers used for calculations.

B. An object is a special keyword used to start a program.

C. An object is a type of function that runs automatically.

D. An object is a combination of data (attributes) and actions (methods) representing something real.

Solution

1. Step 1: Understand what an object represents

   An object models real-world things by holding data and actions together.

2. Step 2: Compare options with this understanding

   Only An object is a combination of data (attributes) and actions (methods) representing something real. correctly describes an object as data plus actions representing something real.

3. Final Answer:

   An object is a combination of data (attributes) and actions (methods) representing something real. -> Option D

4. Quick Check:

   Object = Data + Actions [OK]

Hint: Objects combine data and actions like real things [OK]

Common Mistakes:

• Thinking objects are just lists or numbers
• Confusing objects with functions
• Believing objects are keywords

2. Which of the following is the correct way to define a simple class named Car in Python?

easy

A. class Car()

B. class Car:
pass

C. def Car:
pass

D. Car = class()

Solution

1. Step 1: Recall Python class syntax

   Classes start with the keyword class, followed by the class name and a colon.

2. Step 2: Check each option

   class Car: pass correctly uses class Car: and a body with pass. Others have syntax errors.

3. Final Answer:

   class Car:\n pass -> Option B

4. Quick Check:

   class keyword + name + colon = correct class [OK]

Hint: Use 'class ClassName:' to define a class [OK]

Common Mistakes:

• Using def instead of class
• Missing colon after class name
• Trying to assign class to a variable

3. What will be the output of this code?

class Dog:
    def __init__(self, name):
        self.name = name
    def bark(self):
        return f"{self.name} says Woof!"

my_dog = Dog('Buddy')
print(my_dog.bark())

medium

A. my_dog says Woof!

B. Woof!

C. Buddy says Woof!

D. Error: missing self parameter

Solution

1. Step 1: Understand the class and method

   The Dog class stores the dog's name and the bark method returns a string with the dog's name.

2. Step 2: Trace the code execution

   Creating my_dog = Dog('Buddy') sets self.name to 'Buddy'. Calling my_dog.bark() returns 'Buddy says Woof!'.

3. Final Answer:

   Buddy says Woof! -> Option C

4. Quick Check:

   Method uses self.name = Buddy [OK]

Hint: Methods use self to access object data [OK]

Common Mistakes:

• Ignoring self and expecting just 'Woof!'
• Printing variable name instead of value
• Confusing method call syntax

4. Find the error in this class definition and choose the correct fix:

class Book:
    def __init__(title, author):
        self.title = title
        self.author = author

medium

A. Add 'self' as the first parameter in __init__ method.

B. Change __init__ to init without underscores.

C. Remove self from inside the method.

D. Rename class to book (lowercase).

Solution

1. Step 1: Identify the __init__ method parameters

   The first parameter of any instance method must be self to refer to the object.

2. Step 2: Check the given code

   The __init__ method lacks self as the first parameter, causing an error when assigning attributes.

3. Final Answer:

   Add 'self' as the first parameter in __init__ method. -> Option A

4. Quick Check:

   Instance methods need self first [OK]

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

Common Mistakes:

• Forgetting self in method parameters
• Changing __init__ name incorrectly
• Ignoring case sensitivity in class names

5. You want to model a Library that holds many Book objects. Which design best uses classes to represent this real-world situation?

hard

A. Create a Book class with title and author, and a Library class with a list of Book objects as an attribute.

B. Create only a Library class with title and author attributes.

C. Create a Book class with a list of libraries it belongs to, no Library class.

D. Use a single class named BookLibrary with no separate classes.

Solution

1. Step 1: Understand the real-world relationship

   A library contains many books, so it makes sense to have separate classes for each.

2. Step 2: Check which design models this well

   Create a Book class with title and author, and a Library class with a list of Book objects as an attribute. uses a Book class for individual books and a Library class holding a list of books, matching the real-world model.

3. Final Answer:

   Create a Book class with title and author, and a Library class with a list of Book objects as an attribute. -> Option A

4. Quick Check:

   Separate classes + composition = best model [OK]

Hint: Use separate classes and lists to model collections [OK]

Common Mistakes:

• Combining unrelated data in one class
• Ignoring relationships between objects
• Not using lists to hold multiple objects