Instance attributes in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of instance attribute modification

What is the output of this Python code involving instance attributes?

Python

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

d1 = Dog('Buddy')
d2 = Dog('Max')
d1.name = 'Charlie'
print(d2.name)

A Max

B Charlie

C None

D Buddy

💡 Hint

Each instance has its own attributes. Changing one does not affect the other.

Changing d1.name only changes the name for d1. d2.name remains 'Max'.

❓ Predict Output

intermediate

Instance attribute shadowing class attribute

What will be printed by this code?

Python

class Cat:
    species = 'Felis'

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

c = Cat('Whiskers')
c.species = 'Panthera'
print(Cat.species)
print(c.species)

A Panthera\nPanthera

B Felis\nPanthera

C Felis\nFelis

D Panthera\nFelis

💡 Hint

Instance attribute with the same name hides the class attribute for that instance.

Class attribute Cat.species remains 'Felis'. Instance c.species is set to 'Panthera', shadowing the class attribute.

🔧 Debug

advanced

Identify the error in instance attribute assignment

What error does this code raise when run?

Python

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

p = Person('Alice')
print(p.name)

A TypeError

B NameError

C None (prints 'Alice')

D AttributeError

💡 Hint

Check if the instance attribute is properly assigned inside __init__.

The code assigns to local variable 'name' instead of instance attribute 'self.name'. So p has no 'name' attribute, causing AttributeError.

❓ Predict Output

advanced

Instance attribute default value behavior

What is the output of this code?

Python

class Counter:
    def __init__(self):
        if not hasattr(self, 'count'):
            self.count = 0
    def increment(self):
        self.count += 1

c1 = Counter()
c2 = Counter()
c1.increment()
c1.increment()
c2.increment()
print(c1.count, c2.count)

A 2 1

B 1 1

C 0 0

D 2 2

💡 Hint

Each instance has its own 'count' attribute initialized to 0.

c1 increments twice, so c1.count is 2. c2 increments once, so c2.count is 1.

🧠 Conceptual

expert

Understanding instance attribute creation timing

When is an instance attribute created in Python classes?

A When the attribute is accessed for the first time

B When the class is defined

C When the instance is created and the attribute is assigned

D When the interpreter starts

💡 Hint

Think about when the attribute actually appears on the object.

Instance attributes are created when assigned to self inside methods or after instance creation, not before.