Python Coding challenge - Day 1073| What is the output of the following Python Code?

 

Code Explanation:

1. Defining Class D

class D:

Explanation:

This line creates a class named D.

This class will act as a descriptor.

A descriptor is a class that defines special methods like __get__, __set__, or __delete__ to control attribute access.

2. Defining the __get__ Method

def __get__(self, obj, objtype):

Explanation:

__get__ is a descriptor method.

It is automatically called when the attribute is accessed (read).

Parameters:

self → descriptor object (D)

obj → instance of class A

objtype → the class (A)

When we access a.x, Python internally calls:

D.__get__(descriptor, a, A)

3. Returning a Value

return 50

Explanation:

Whenever x is accessed through an object, this method returns 50.

So the descriptor controls the value returned.

Meaning:

a.x → 50

4. Defining Class A

class A:

Explanation:

This creates another class named A.

5. Creating Descriptor Attribute

x = D()

Explanation:

Here an object of class D is assigned to attribute x.

This makes x a descriptor attribute.

Accessing x will trigger the __get__ method.

So:

A.x → descriptor object of class D

6. Creating an Object

a = A()

Explanation:

This creates an instance a of class A.

7. Adding Attribute Directly to Object Dictionary

a.__dict__['x'] = 20

Explanation:

__dict__ stores all instance attributes of an object.

This line manually adds an attribute:

x = 20

inside the object's dictionary.

So internally:

a.__dict__ = {'x': 20}

8. Printing a.x

print(a.x)

Explanation:

Python checks attributes in this order:

Data descriptor (__get__ + __set__)

Instance dictionary

Non-data descriptor (__get__ only)

Class attributes

Here:

D defines only __get__, so it is a non-data descriptor.

Python first checks instance dictionary.

It finds:

a.__dict__['x'] = 20

So Python returns 20 instead of calling the descriptor.

9. Final Output

20

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