Python Coding challenge - Day 1144| What is the output of the following Python Code?

 

Code Explanation:

🔹 1. Creating Empty List

a = []

✅ Explanation:

An empty list a is created.

It will store inner lists.

🔹 2. Loop to Add Inner Lists

for i in range(3):

    a.append([i])

✅ Explanation:

Loop runs for: i = 0, 1, 2

Each time, a new list [i] is created and appended

🔍 After loop:

a → [[0], [1], [2]]

✔️ Important:

Each inner list is a separate object in memory

🔹 3. Shallow Copy

b = a.copy()

✅ Explanation:

Creates a shallow copy of list a

Only the outer list is copied

Inner lists are still shared

🔍 So:

b → [[0], [1], [2]]

But:

b[0] is a[0] → True

👉 Both point to same inner list

🔹 4. Modifying Copied List

b[0][0] = 100

✅ Explanation:

Accesses:

b[0] → first inner list [0]

Then changes its first element → 100

🔍 Now:

b → [[100], [1], [2]]

🔹 5. Why a Also Changes

Since:

b[0] is a[0]

👉 The same inner list is modified

So:

a → [[100], [1], [2]]

🔹 6. Printing Original List

print(a)

✅ Output:

[[100], [1], [2]]

🎯 Final Output

[[100], [1], [2]]

Book: 900 Days Python Coding Challenges with Explanation