Find and Fix Mistakes – Python Inheritance Practice Questions.

Practice Python OOP inheritance by identifying and fixing common mistakes in code examples.

1. Question:

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

class Child(Father):
    pass

c = Child("Ali")
print(c.name)

What’s the mistake? How would you fix it?

Mistake:
The name parameter is assigned to itself; it should be assigned to an instance variable.

Fix:

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

2. Question:

class Animal:
    def sound():
        print("Some sound")

class Dog(Animal):
    pass

d = Dog()
d.sound()

What’s the mistake? How would you fix it?

Mistake:
The sound method is missing the self parameter.

Fix:

class Animal:
    def sound(self):
        print("Some sound")

3. Question:

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

class Student(Person):
    def __init__(self, school):
        self.school = school

What’s the mistake? How would you fix it?

Mistake:
The Student class overrides the constructor without calling the parent’s constructor.

Fix:

class Student(Person):
    def __init__(self, name, school):
        super().__init__(name)
        self.school = school

4. Question:

class A:
    def show(self):
        print("Class A")

class B(A):
    def show(self):
        print("Class B")

obj = A()
obj.show()

Mistake Prompt:
Change the code so that an object of B calls the show method of A.

Fix:
Use super() or explicitly call A.show(self) inside class B:

class B(A):
    def show(self):
        super().show()

Here are 10 Python inheritance code questions with intentional mistakes. Learners need to identify/fix the errors:

Q1: Missing Super Initialization

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

class Car(Vehicle):
    def __init__(self, model):
        self.model = model  # Error: Forgot super().__init__

car = Car("Tesla", "Model S")  # Throws error

Error: Car doesn’t call Vehicle.__init__
Fix: Add super().__init__(brand) in Car.__init__

Q2: Method Override Gone Wrong

class Parent:
    def show(self):
        print("Parent method")

class Child(Parent):
    def show(self):
        print("Child method")  # Error: Parent method not called

child = Child()
child.show()  # Only shows "Child method"

Error: Parent method not preserved
Fix: Add super().show() in Child’s show()

Q3: Multiple Inheritance MRO Confusion

class Parent1:
    def display(self):
        print("Parent1")

class Parent2:
    def display(self):
        print("Parent2")

class Child(Parent1, Parent2):
    pass  # Which display() is called?

obj = Child()
obj.display()  # Outputs "Parent1" - is this intended?

Mistake: Parent order might be unexpected
Test: Change inheritance order to (Parent2, Parent1)

Q4: Private Variable Access

class Base:
    def __init__(self):
        self.__secret = 123  # Name mangled

class Derived(Base):
    def get_secret(self):
        return self.__secret  # Error: AttributeError

d = Derived()
print(d.get_secret())

Error: Can’t access __secret directly in subclass
Fix: Use _Base__secret or make it protected (_secret)

Q5: Inheritance vs Composition

class Engine:
    def start(self):
        print("Engine started")

class Car(Engine):  # Bad inheritance
    def drive(self):
        self.start()

car = Car()
car.drive()  # Works but poor design

Mistake: Car isn’t an Engine subtype
Fix: Use composition (self.engine = Engine())

Q6: Static Method Inheritance

class MathOps:
    @staticmethod
    def add(a, b):
        return a + b

class AdvancedMath(MathOps):
    def add(a, b, c):  # Missing @staticmethod
        return a + b + c

result = AdvancedMath.add(1, 2, 3)  # TypeError

Error: Forgot @staticmethod decorator
Fix: Add @staticmethod above AdvancedMath.add

Q7: Diamond Problem in Python

class A:
    def __init__(self):
        print("A initialized")

class B(A):
    def __init__(self):
        super().__init__()
        print("B initialized")

class C(A):
    def __init__(self):
        super().__init__()
        print("C initialized")

class D(B, C):
    def __init__(self):
        super().__init__()  # Initializes B -> C -> A
        print("D initialized")

d = D()  # Output order might surprise beginners

Test: Analyze MRO with print(D.__mro__)

Q8: Property Override Failure

class Account:
    @property
    def balance(self):
        return self._balance

class Savings(Account):
    def balance(self):  # Forgot @property
        return self._balance * 1.05  # Broken

sa = Savings()
sa.balance  # Throws AttributeError

Error: balance becomes method, not property
Fix: Add @property decorator in Savings

Q9: Parent Argument Mismatch

class Shape:
    def __init__(self, color):
        self.color = color

class Circle(Shape):
    def __init__(self, radius):
        super().__init__()  # Error: Missing color arg
        self.radius = radius

c = Circle("red", 5)  # TypeError

Fix: super().__init__(color) + adjust parameters

Q10: Inheriting Non-Class

name = "BaseClass"

class MyClass(name):  # Error: 'str' is not a class
    pass

Mistake: Trying to inherit from string
Fix: Inherit from proper base class (e.g., object)