Python Coding challenge - Day 1058| What is the output of the following Python Code?

 

Code Explanation:

1. Defining Class A

class A:

    x = "A"

Creates base class A

Defines a class attribute x with value "A"

All subclasses inherit this attribute unless overridden

🔹 2. Defining Class B (Overrides x)

class B(A):

    x = None

B inherits from A

Redefines x and assigns it None

This overrides A.x inside class B

📌 Important:

Setting x = None is still a valid override, not a removal.

🔹 3. Defining Class C (No Override)

class C(A):

    pass

C inherits from A

Does not define x

So C.x is inherited from A

📌 C.x → "A"

🔹 4. Defining Class D (Multiple Inheritance)

class D(B, C):

    pass

D inherits from both B and C

Does not define x

Python must decide which parent’s x to use

➡️ Python uses Method Resolution Order (MRO)

🔹 5. MRO of Class D

D.mro()

Result:

[D, B, C, A, object]

📌 Attribute lookup follows this order:

D

B

C

A

object

🔹 6. Attribute Lookup for D.x

print(D.x)

Step-by-step:

D → ❌ no x

B → ✅ x = None found

Lookup stops immediately

📌 Python does not continue to C or A

✅ Final Output

None

700 Days Python Coding Challenges with Explanation