Comparison magic methods in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of custom __eq__ method

What is the output of this code?

Python

class Box:
    def __init__(self, volume):
        self.volume = volume
    def __eq__(self, other):
        return self.volume == other.volume

b1 = Box(10)
b2 = Box(10)
b3 = Box(5)

print(b1 == b2)
print(b1 == b3)

A False\nTrue

B False\nFalse

C True\nTrue

D True\nFalse

💡 Hint

The __eq__ method compares the volume attribute of two Box objects.

The __eq__ method returns True if the volumes are equal. b1 and b2 have volume 10, so b1 == b2 is True. b1 and b3 have different volumes, so b1 == b3 is False.

❓ Predict Output

intermediate

Output of __lt__ and __gt__ methods

What is the output of this code?

Python

class Number:
    def __init__(self, value):
        self.value = value
    def __lt__(self, other):
        return self.value < other.value
    def __gt__(self, other):
        return self.value > other.value

n1 = Number(3)
n2 = Number(5)
print(n1 < n2)
print(n1 > n2)

A True\nFalse

B False\nFalse

C True\nTrue

D False\nTrue

💡 Hint

The __lt__ method checks if one value is less than the other, __gt__ checks if greater.

n1.value is 3 and n2.value is 5. 3 < 5 is True, 3 > 5 is False.

❓ Predict Output

advanced

Output of __le__ and __ge__ with inheritance

What is the output of this code?

Python

class Base:
    def __init__(self, x):
        self.x = x
    def __le__(self, other):
        return self.x <= other.x
    def __ge__(self, other):
        return self.x >= other.x

class Derived(Base):
    pass

b = Base(7)
d = Derived(7)
print(b <= d)
print(b >= d)

A True\nTrue

B False\nTrue

C True\nFalse

D False\nFalse

💡 Hint

Derived inherits comparison methods from Base and both have the same x value.

Both b and d have x = 7. So b <= d and b >= d both return True.

❓ Predict Output

advanced

Output of __eq__ with different types

What is the output of this code?

Python

class Item:
    def __init__(self, id):
        self.id = id
    def __eq__(self, other):
        if not isinstance(other, Item):
            return False
        return self.id == other.id

item = Item(10)
print(item == 10)
print(item == Item(10))

A True\nTrue

B False\nFalse

C False\nTrue

D True\nFalse

💡 Hint

The __eq__ method returns False if the other object is not an Item instance.

item == 10 returns False because 10 is not an Item. item == Item(10) returns True because ids match.

❓ Predict Output

expert

Output of chained comparisons with custom __lt__

What is the output of this code?

Python

class Weird:
    def __init__(self, val):
        self.val = val
    def __lt__(self, other):
        print(f"Comparing {self.val} < {other.val}")
        return self.val < other.val

w1 = Weird(1)
w2 = Weird(2)
w3 = Weird(3)
print(w1 < w2 < w3)

A Comparing 1 < 2\nComparing 2 < 3\nFalse

B Comparing 1 < 2\nComparing 2 < 3\nTrue

C Comparing 1 < 2\nTrue

D Comparing 1 < 2\nComparing 3 < 2\nTrue

💡 Hint

Python evaluates chained comparisons by checking each pair separately.

The expression w1 < w2 < w3 calls __lt__ twice: w1 < w2 and w2 < w3. Both print statements appear, and since 1 < 2 and 2 < 3 are True, the final output is True.