Adding custom attributes in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of adding a custom attribute to a class instance?

Consider the following Python code where we add a custom attribute to an instance of a class. What will be printed?

Python

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

my_car = Car('Toyota')
my_car.color = 'red'
print(my_car.color)

A AttributeError

B Toyota

C red

D None

💡 Hint

Think about what happens when you add a new attribute directly to an instance.

The attribute color is added directly to the instance my_car. So printing my_car.color outputs 'red'.

❓ Predict Output

intermediate

What happens when you add a custom attribute to a class itself?

Look at this code where a custom attribute is added to the class, not the instance. What will be the output?

Python

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

Dog.legs = 4
buddy = Dog('Buddy')
print(buddy.legs)

A None

B 4

C AttributeError

D 0

💡 Hint

Remember that instances can access class attributes if they don't have their own.

The attribute legs is added to the class Dog. The instance buddy can access it, so printing buddy.legs outputs 4.

❓ Predict Output

advanced

What error occurs when accessing a missing custom attribute?

What error will this code produce when trying to print a missing attribute?

Python

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

novel = Book('1984')
print(novel.author)

A KeyError

B NameError

C TypeError

D AttributeError

💡 Hint

Think about what happens when you try to access an attribute that was never set.

Since author was never set on the instance or class, Python raises an AttributeError.

🧠 Conceptual

advanced

How to add a custom attribute to all instances of a class after creation?

You want to add a new attribute category to all existing and future instances of a class Product. Which approach works?

A Add <code>Product.category = 'general'</code> after instances are created

B Add <code>self.category = 'general'</code> inside <code>__init__</code> method

C Add <code>product.category = 'general'</code> for each instance separately

D Add <code>del Product.category</code> after instances are created

💡 Hint

Think about class attributes and how instances access them.

Adding category as a class attribute after instances exist makes it accessible to all instances unless overridden.

❓ Predict Output

expert

What is the output after modifying a custom attribute on one instance?

Given this code, what will be printed?

Python

class Employee:
    department = 'Sales'

emp1 = Employee()
emp2 = Employee()

emp1.department = 'Marketing'
print(emp2.department)

A Sales

B Marketing

C AttributeError

D None

💡 Hint

Remember the difference between instance and class attributes.

Changing emp1.department creates an instance attribute for emp1 only. emp2.department still refers to the class attribute 'Sales'.