Public attributes in Python - Mini Project: Build & Apply

Understanding Public Attributes in Python Classes

📖 Scenario: Imagine you are creating a simple program to manage a library's books. Each book has a title and an author. You want to store this information in a class and be able to access it easily.

🎯 Goal: You will create a Python class with public attributes for the book's title and author. Then, you will create an object of this class and print its attributes.

📋 What You'll Learn

Create a class named Book with public attributes title and author

Create an object of the Book class with the title 'The Great Gatsby' and author 'F. Scott Fitzgerald'

Access and print the title and author attributes of the object

💡 Why This Matters

🌍 Real World

Public attributes are used to store and access information about objects in many programs, such as managing books in a library or products in a store.

💼 Career

Understanding how to use public attributes is a basic skill for programming jobs that involve object-oriented programming, such as software development and data modeling.

1

Create the Book class with public attributes

Create a class called Book with an __init__ method that takes title and author as parameters and assigns them to public attributes self.title and self.author.

Python

# Define the Book class with __init__ method
# Your code here

Hint

Remember, public attributes are created by assigning values to self.attribute_name inside the __init__ method.

2

Create a Book object with specific title and author

Create an object called my_book from the Book class with the title 'The Great Gatsby' and author 'F. Scott Fitzgerald'.

Python

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

# Create the my_book object
# Your code here

Hint

Use the class name Book followed by parentheses with the title and author strings inside to create the object.

3

Access the public attributes of the my_book object

Write two lines of code to assign the title attribute of my_book to a variable called book_title and the author attribute to a variable called book_author.

Python

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

my_book = Book('The Great Gatsby', 'F. Scott Fitzgerald')

# Assign the attributes to variables
# Your code here

Hint

Use dot notation like object.attribute to access public attributes.

4

Print the book's title and author

Print the values of book_title and book_author on separate lines.

Python

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

my_book = Book('The Great Gatsby', 'F. Scott Fitzgerald')

book_title = my_book.title
book_author = my_book.author

# Print the title and author
# Your code here

Hint

Use two print() statements, one for each variable.

Practice

1. What is a public attribute in a Python class?

easy

A. An attribute that can be accessed and changed from outside the class

B. An attribute that is hidden and cannot be accessed outside the class

C. A method that runs automatically when an object is created

D. A special function to delete an object

Solution

1. Step 1: Understand attribute visibility

   Public attributes are designed to be accessed and modified from outside the class.

2. Step 2: Compare options

   An attribute that can be accessed and changed from outside the class correctly describes public attributes. Options A, B, and D describe other concepts.

3. Final Answer:

   An attribute that can be accessed and changed from outside the class -> Option A

4. Quick Check:

   Public attribute = accessible outside [OK]

Hint: Public means anyone can access or change it [OK]

Common Mistakes:

• Confusing public with private attributes
• Thinking methods are attributes
• Mixing up constructors with attributes

2. Which of the following is the correct way to create a public attribute name inside a Python class constructor?

easy

A. self->name = value

B. self.name = value

C. name = self.value

D. def name(self):

Solution

1. Step 1: Recall syntax for public attributes

   Inside __init__, public attributes are created by assigning to self.attribute_name.

2. Step 2: Check each option

   self.name = value uses correct syntax: self.name = value. Others are invalid Python syntax or wrong usage.

3. Final Answer:

   self.name = value -> Option B

4. Quick Check:

   Use self.attribute = value [OK]

Hint: Use self.attribute = value inside __init__ [OK]

Common Mistakes:

• Using def instead of assignment
• Wrong arrow syntax like self->name
• Assigning attribute to name instead of self.name

3. What will be the output of this code?

class Dog:
    def __init__(self, name):
        self.name = name

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

medium

A. Dog

B. Error

C. my_dog

D. Buddy

Solution

1. Step 1: Understand attribute assignment

   The constructor sets self.name to the value passed, which is 'Buddy'.

2. Step 2: Print the attribute value

   Printing my_dog.name outputs 'Buddy'.

3. Final Answer:

   Buddy -> Option D

4. Quick Check:

   Print attribute value = Buddy [OK]

Hint: Print object.attribute to see stored value [OK]

Common Mistakes:

• Expecting class name instead of attribute value
• Confusing object name with attribute
• Thinking it causes an error

4. Find the error in this code that tries to create a public attribute age:

class Person:
    def __init__(self, age):
        age = age

p = Person(30)
print(p.age)

medium

A. The attribute should be assigned to self.age, not age

B. The print statement should be print(age)

C. The constructor is missing a return statement

D. The class name should be lowercase

Solution

1. Step 1: Check attribute assignment

   Assigning age = age only creates a local variable, not an attribute of the object.

2. Step 2: Correct attribute assignment

   It should be self.age = age to create a public attribute accessible outside.

3. Final Answer:

   The attribute should be assigned to self.age, not age -> Option A

4. Quick Check:

   Use self.attribute = value to create public attribute [OK]

Hint: Always assign attributes to self.attribute inside __init__ [OK]

Common Mistakes:

• Assigning to local variable instead of self.attribute
• Trying to print variable not attached to object
• Thinking constructor needs return

5. You want to create a class Car that stores the public attributes make and year. Which code correctly creates these attributes and allows access to them?

hard

A. class Car:
def __init__(self, make, year):
self.make = make
year = self.year

my_car = Car('Toyota', 2020)
print(my_car.make, my_car.year)

B. class Car:
def __init__(self, make, year):
make = self.make
year = self.year

my_car = Car('Toyota', 2020)
print(my_car.make, my_car.year)

C. class Car:
def __init__(self, make, year):
self.make = make
self.year = year

my_car = Car('Toyota', 2020)
print(my_car.make, my_car.year)

D. class Car:
def __init__(self, make, year):
self.make = make
self.year = year

my_car = Car('Toyota', 2020)
print(make, year)

Solution

1. Step 1: Check attribute assignments

   class Car: def __init__(self, make, year): self.make = make self.year = year my_car = Car('Toyota', 2020) print(my_car.make, my_car.year) correctly assigns self.make and self.year to the passed values.

2. Step 2: Check attribute access

   class Car: def __init__(self, make, year): self.make = make self.year = year my_car = Car('Toyota', 2020) print(my_car.make, my_car.year) prints my_car.make and my_car.year, which are valid public attributes.

3. Final Answer:

   class Car: def __init__(self, make, year): self.make = make self.year = year my_car = Car('Toyota', 2020) print(my_car.make, my_car.year) -> Option C

4. Quick Check:

   Assign and access via self.attribute and object.attribute [OK]

Hint: Assign attributes to self and access via object.attribute [OK]

Common Mistakes:

• Assigning attributes backwards (make = self.make)
• Accessing attributes without object prefix
• Mixing local variables with attributes