Python Coding challenge - Day 940| What is the output of the following Python Code?

 

Code Explanation:

1. Defining the Base Class

class A: 

    pass

Class A is defined.

It has no methods or attributes.

It serves as the common base class.

2. Defining Subclasses of A

class B(A): 

    pass

class C(A): 

    pass

Class B inherits from A.

Class C also inherits from A.

So both B and C are direct children of A.

Inheritance structure so far:

A

├── B

└── C

3. Defining a Class with Multiple Inheritance

class D(B, C): 

    pass

Class D inherits from both B and C.

Order matters: B is listed before C.

So the hierarchy becomes:

      A

     / \

    B   C

     \ /

      D

4. Calling the MRO Method

print([cls.__name__ for cls in D.mro()])

D.mro() returns the Method Resolution Order, which is the order Python uses to search for attributes and methods.

It uses the C3 linearization algorithm to compute a consistent order.

5. How Python Computes the MRO

Python merges the MROs of the parent classes while:

Preserving the order of base classes (B before C)

Ensuring each class appears before its parents

MRO calculation:

D.mro() = [D] + merge(B.mro(), C.mro(), [B, C])

Where:

B.mro() = [B, A, object]

C.mro() = [C, A, object]

Merge result:

[D, B, C, A, object]

6. Final Output

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

Final Answer

✔ Output:

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

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