Python Coding challenge - Day 1276| What is the output of the following Python Code?

 

Code Explanation:

1. 🏗️ Create the Descriptor Class

class D:

A class D is created.

This class will act as a descriptor because it defines the special method __get__().

2. 🔍 Define __get__()

def __get__(self, obj, owner):

__get__() controls what happens when the descriptor attribute is read.

Here:

- obj → the instance accessing the attribute

- owner → the class that owns the descriptor

For a.x:

obj   → a

owner → A

3. 🎯 Return 50

return 50

Whenever the descriptor's value is retrieved, it returns:

50

So the descriptor does not return the value stored in the instance dictionary.

4. 📌 Put Descriptor in Class A

class A:    x = D()

Here:

A.x → D object

The object created by D() is assigned to A.x.

Because D defines __get__(), x becomes a descriptor.

5. 🆕 Create Object a

a = A()

An instance of A is created.

At this point, a doesn't have an "x" entry in its own __dict__.

6. 📝 Manually Add x to a.__dict__

a.__dict__["x"] = 100

Now the instance dictionary contains:

a.__dict__

which is approximately:

{'x': 100}

So it may look like:

a.x

should return 100.

But there is an important descriptor rule.

7. ⚡ Access a.x

print(a.x)

Python sees that A.x is a non-data descriptor because D has __get__() but does not have __set__() or __delete__().

Normally, an instance attribute can override a non-data descriptor.

So in fact, this code:

a.__dict__["x"] = 100

means the instance value wins.

Therefore:

a.x → 100

✅ Correct Final Output

100

Books: 400 Days Python Coding Challenges with Explanation