String representation methods in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of __str__ vs __repr__

What is the output of the following code?

Python

class Fruit:
    def __init__(self, name):
        self.name = name
    def __str__(self):
        return f"Fruit: {self.name}"
    def __repr__(self):
        return f"Fruit('{self.name}')"

f = Fruit('Apple')
print(str(f))
print(repr(f))

A

Fruit: Apple
Apple

B

Fruit('Apple')
Fruit: Apple

C

Apple
Fruit('Apple')

D

Fruit: Apple
Fruit('Apple')

💡 Hint

Remember __str__ is for user-friendly display, __repr__ is for developer-friendly output.

The str() function calls __str__ which returns 'Fruit: Apple'. The repr() function calls __repr__ which returns 'Fruit('Apple')'.

❓ Predict Output

intermediate

Using __repr__ in a list

What is the output of this code?

Python

class Animal:
    def __init__(self, species):
        self.species = species
    def __repr__(self):
        return f"Animal('{self.species}')"

animals = [Animal('Cat'), Animal('Dog')]
print(animals)

A [Animal('Cat'), Animal('Dog')]

B ['Cat', 'Dog']

C [Animal(Cat), Animal(Dog)]

D [<Animal object>, <Animal object>]

💡 Hint

Lists use __repr__ of their elements when printed.

When printing a list, Python calls __repr__ on each element. So it shows the string returned by __repr__ of each Animal.

🔧 Debug

advanced

Fix the __str__ method to avoid error

This code raises an error when printing the object. Which option fixes the error?

Python

class Book:
    def __init__(self, title):
        self.title = title
    def __str__(self):
        return 'Book title is ' + self.title.upper

b = Book('Python 101')
print(b)

A

def __str__(self):
    return 'Book title is ' + self.title.upper()

B

def __str__(self):
    return 'Book title is ' + str(self.title.upper)

C

def __str__(self):
    return 'Book title is ' + self.title.upper

D

def __str__(self):
    return 'Book title is ' + self.title

💡 Hint

Check if you are calling the method or just referencing it.

The error happens because self.title.upper is a method, not a string. You must call it with parentheses: self.title.upper().

🧠 Conceptual

advanced

Difference between __str__ and __repr__

Which statement best describes the difference between __str__ and __repr__ methods in Python?

A <code>__str__</code> is only used when printing lists; <code>__repr__</code> is used everywhere else.

B <code>__str__</code> is for a readable string for users; <code>__repr__</code> is for unambiguous string for developers.

C Both methods return the same string but <code>__repr__</code> is faster.

D <code>__repr__</code> is for readable string for users; <code>__str__</code> is for debugging.

💡 Hint

Think about who the string is for: user or developer.

__str__ returns a friendly string for users, while __repr__ returns a detailed string useful for developers to identify the object.

❓ Predict Output

expert

Output of custom __repr__ with eval

What is the output of this code?

Python

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y
    def __repr__(self):
        return f"Point({self.x}, {self.y})"

p = Point(3, 4)
q = eval(repr(p))
print(p == q)
print(q)

A

False
<__main__.Point object at 0x...>

B

True
Point(3, 4)

C

False
Point(3, 4)

D

True
<__main__.Point object at 0x...>

💡 Hint

Does eval(repr(p)) create an equal object? What about equality check?

The repr returns 'Point(3, 4)', but eval tries to call Point(3, 4). Since Point constructor exists, q is a new object with same values but different identity. The default == compares identity, so p == q is False.