Multiple inheritance syntax in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of multiple inheritance method call

What is the output of this Python code using multiple inheritance?

Python

class A:
    def greet(self):
        return "Hello from A"

class B:
    def greet(self):
        return "Hello from B"

class C(A, B):
    pass

obj = C()
print(obj.greet())

A Hello from A

B Hello from B

C Hello from C

D TypeError

💡 Hint

Remember Python uses method resolution order (MRO) and looks for methods in the first parent class listed.

Class C inherits from A and B. Since A is listed first, its greet method is used.

❓ Predict Output

intermediate

Output when overriding method in multiple inheritance

What will this code print?

Python

class X:
    def action(self):
        return "Action from X"

class Y:
    def action(self):
        return "Action from Y"

class Z(X, Y):
    def action(self):
        return super().action()

obj = Z()
print(obj.action())

A Action from X

B AttributeError

C Action from Z

D Action from Y

💡 Hint

super() in class Z calls the next method in the MRO after Z.

super() calls X's action method because X is the first parent in the MRO after Z.

❓ Predict Output

advanced

Output of diamond inheritance with super()

What is the output of this code involving diamond inheritance?

Python

class Base:
    def greet(self):
        return "Hello from Base"

class Left(Base):
    def greet(self):
        return "Left says " + super().greet()

class Right(Base):
    def greet(self):
        return "Right says " + super().greet()

class Child(Left, Right):
    def greet(self):
        return "Child says " + super().greet()

obj = Child()
print(obj.greet())

A Child says Left says Hello from Base

B Child says Right says Left says Hello from Base

C Child says Left says Right says Hello from Base

D TypeError

💡 Hint

Check the method resolution order (MRO) for Child and how super() calls chain.

The MRO is Child > Left > Right > Base. Each greet calls super().greet(), so the output chains accordingly.

❓ Predict Output

advanced

Error raised by incorrect multiple inheritance syntax

What error does this code raise?

Python

class A:
    pass

class B:
    pass

class C(A, B):
    pass

A No error

B TypeError

C NameError

D SyntaxError

💡 Hint

Check the syntax for listing multiple parent classes.

Parent classes must be separated by commas. Missing comma causes SyntaxError.

🧠 Conceptual

expert

Order of classes in multiple inheritance affects method resolution

Given these classes, which option shows the correct method resolution order (MRO) for class D?

class A: pass
class B(A): pass
class C(A): pass
class D(B, C): pass

A [D, A, B, C, object]

B [D, B, C, A, object]

C [D, C, B, A, object]

D [D, B, A, C, object]

💡 Hint

Python uses C3 linearization for MRO. The order of parents in class D matters.

For class D(B, C), MRO is D, B, C, A, object. B before C because B is listed first.

Practice

1. What is the correct way to declare a class Child that inherits from two parent classes Parent1 and Parent2 in Python?

easy

A. class Child(Parent1, Parent2):

B. class Child(Parent1 & Parent2):

C. class Child inherits Parent1, Parent2:

D. class Child: Parent1, Parent2

Solution

1. Step 1: Understand Python class inheritance syntax

   In Python, to inherit from multiple classes, list them separated by commas inside parentheses after the class name.

2. Step 2: Match the syntax to the options

   class Child(Parent1, Parent2): uses the correct syntax: class Child(Parent1, Parent2):. Other options use invalid syntax.

3. Final Answer:

   class Child(Parent1, Parent2): -> Option A

4. Quick Check:

   Multiple inheritance syntax = class Child(Parent1, Parent2): [OK]

Hint: List parent classes separated by commas in parentheses [OK]

Common Mistakes:

• Using '&' instead of commas between parent classes
• Writing 'inherits' keyword like other languages
• Not using parentheses after class name

2. Which of the following is a syntax error when defining a class with multiple inheritance?

easy

A. class MyClass(): pass

B. class MyClass(Parent1, Parent2): pass

C. class MyClass(Parent1): pass

D. class MyClass(Parent1 Parent2): pass

Solution

1. Step 1: Check syntax for multiple inheritance

   Parent classes must be separated by commas inside parentheses.

2. Step 2: Identify the incorrect option

   class MyClass(Parent1 Parent2): pass misses the comma between Parent1 and Parent2, causing a syntax error.

3. Final Answer:

   class MyClass(Parent1 Parent2): pass -> Option D

4. Quick Check:

   Missing comma between parents = SyntaxError [OK]

Hint: Always separate parent classes with commas [OK]

Common Mistakes:

• Omitting commas between parent classes
• Leaving out parentheses entirely
• Using colons instead of commas

3. What will be the output of this code?

class A:
    def greet(self):
        return "Hello from A"

class B:
    def greet(self):
        return "Hello from B"

class C(A, B):
    pass

obj = C()
print(obj.greet())

medium

A. "Hello from A"

B. TypeError

C. AttributeError

D. "Hello from B"

Solution

1. Step 1: Understand method resolution order (MRO)

   Class C inherits from A first, then B. Python looks for methods in the order of parents listed.

2. Step 2: Determine which greet() is called

   Since A is first, C uses A's greet method, returning "Hello from A".

3. Final Answer:

   "Hello from A" -> Option A

4. Quick Check:

   MRO follows parent order = "Hello from A" [OK]

Hint: First parent class method is used in multiple inheritance [OK]

Common Mistakes:

• Assuming last parent class method is called
• Expecting an error due to multiple parents
• Confusing method names or forgetting MRO

4. Find the error in this multiple inheritance code:

class X:
    pass

class Y:
    pass

class Z(X Y):
    pass

medium

A. Missing colon after class name

B. Missing comma between parent classes

C. Parent classes must be in square brackets

D. Class Z cannot inherit from X and Y

Solution

1. Step 1: Check syntax for multiple inheritance

   Parent classes must be separated by commas inside parentheses.

2. Step 2: Identify the syntax error

   In class Z(X Y):, the comma between X and Y is missing, causing a syntax error.

3. Final Answer:

   Missing comma between parent classes -> Option B

4. Quick Check:

   Comma missing between parents = SyntaxError [OK]

Hint: Separate parent classes with commas inside parentheses [OK]

Common Mistakes:

• Forgetting commas between parent classes
• Using square brackets instead of parentheses
• Thinking multiple inheritance is not allowed

5. Given these classes:

class Alpha:
    def action(self):
        return "Alpha"

class Beta:
    def action(self):
        return "Beta"

class Gamma(Alpha, Beta):
    def action(self):
        return super().action() + " & Gamma"

class Delta(Gamma, Beta):
    pass

obj = Delta()
print(obj.action())

What is the output?

hard

A. "Beta & Gamma"

B. "Gamma"

C. "Alpha & Gamma"

D. AttributeError

Solution

1. Step 1: Understand the inheritance chain and MRO

   Delta inherits from Gamma and Beta. Gamma inherits from Alpha and Beta. The MRO for Delta is Delta, Gamma, Alpha, Beta, object.

2. Step 2: Trace the action() method call

   Delta uses Gamma's action(), which calls super().action(). In Gamma, super() refers to Alpha (next in MRO), so Alpha.action() returns "Alpha". Then Gamma appends " & Gamma".

3. Final Answer:

   "Alpha & Gamma" -> Option C

4. Quick Check:

   super() follows MRO = "Alpha & Gamma" [OK]

Hint: super() calls next in MRO, not just first parent [OK]

Common Mistakes:

• Assuming super() calls Beta's method instead of Alpha's
• Ignoring MRO order in multiple inheritance
• Expecting an error due to complex inheritance