Python Coding challenge - Day 1121| What is the output of the following Python Code?

 

Code Explanation:

1. Class Definition Phase

class Test:

    x = 10

✅ What happens:

A class named Test is created.

A class variable x is defined and assigned value 10.

👉 At this point:

Test.x = 10

📌 2. Constructor (__init__) Definition

def __init__(self):

    self.x = self.x + 5

✅ What happens:

This runs every time an object is created.

self.x refers to:

First tries instance variable

If not found → falls back to class variable

📌 3. Creating First Object (t1)

t1 = Test()

Step-by-step:

🔹 Step 1: Object is created

Python creates a new object t1.

🔹 Step 2: __init__ runs

self.x = self.x + 5

self.x → no instance variable yet

So Python looks at class variable → Test.x = 10

👉 Calculation:

self.x = 10 + 5 = 15

🔹 Step 3: Instance variable created

Now:

t1.x = 15   (instance variable)

📌 4. Creating Second Object (t2)

t2 = Test()

Step-by-step:

Same process repeats:

self.x → still no instance variable

Uses class variable again → 10

👉 Calculation:

self.x = 10 + 5 = 15

Now:

t2.x = 15

📌 5. Important Concept: Class vs Instance Variable

At this point:

Variable Value

Test.x 10

t1.x 15

t2.x 15

👉 Key idea:

self.x = ... creates a new instance variable

It does NOT modify the class variable

📌 6. Final Print Statement

print(t1.x, t2.x, Test.x)

Values:

t1.x → 15

t2.x → 15

Test.x → 10

✅ Final Output

15 15 10

Book:  700 Days Python Coding Challenges with Explanation