Purpose of magic methods in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this code using __str__ magic method?

Consider the following Python class with a magic method. What will be printed when the code runs?

Python

class Book:
    def __init__(self, title):
        self.title = title
    def __str__(self):
        return f"Book title: {self.title}"

b = Book("Python Basics")
print(b)

A <__main__.Book object at 0x...>

B Book title: Python Basics

C Python Basics

D Error: __str__ method missing

💡 Hint

The __str__ method controls what print shows for an object.

The __str__ magic method defines the string representation of an object when printed. Here, it returns 'Book title: Python Basics'.

❓ Predict Output

intermediate

What does this code print using __len__ magic method?

Look at this class with a __len__ method. What will print when len(obj) is called?

Python

class Basket:
    def __init__(self, items):
        self.items = items
    def __len__(self):
        return len(self.items)

obj = Basket(['apple', 'banana', 'cherry'])
print(len(obj))

A 0

B Error: __len__ method not found

C ['apple', 'banana', 'cherry']

D 3

💡 Hint

The __len__ method tells Python how to get the length of an object.

The __len__ magic method returns the length of the items list, which has 3 elements.

🧠 Conceptual

advanced

Why use magic methods like __add__ in classes?

What is the main purpose of defining magic methods such as __add__ in a Python class?

A To prevent the class from being instantiated

B To make the class run faster

C To allow objects of the class to use operators like + in a custom way

D To automatically generate documentation for the class

💡 Hint

Think about what happens when you use + between two objects.

Magic methods like __add__ let you define how operators like + behave with your objects, enabling custom addition behavior.

❓ Predict Output

advanced

What error does this code raise without __eq__ magic method?

What happens when you compare two objects of this class without defining __eq__?

Python

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y

p1 = Point(1, 2)
p2 = Point(1, 2)
print(p1 == p2)

A False

B True

C TypeError

D SyntaxError

💡 Hint

Without __eq__, == compares object identity, not content.

Without __eq__, == checks if both variables point to the same object, which they do not, so it returns False.

🧠 Conceptual

expert

Which magic method allows an object to be used as a context manager?

To use an object with the 'with' statement, which magic methods must the class implement?

A __enter__ and __exit__

B __init__ and __del__

C __call__ and __repr__

D __str__ and __len__

💡 Hint

The 'with' statement needs special methods to start and end the block.

The __enter__ and __exit__ magic methods define what happens when entering and exiting a 'with' block, enabling context management.