Python Coding Challenge - Question with Answer (ID -140526)

 

Explanation:

🔹 Step 1: Create List Reference

x = y = [1]

⚠️ Important:

Both x and y point to SAME list in memory.

Visual:

x ─┐

   ├──> [1]

y ─┘

👉 Current value:

x = [1]

y = [1]

🔹 Step 2: Execute x += [2]

x += [2]

This is equivalent to:

x.extend([2])

⚠️ += modifies list IN-PLACE.

So original shared list changes.

Visual:

x ─┐

   ├──> [1,2]

y ─┘

👉 Now:

x = [1,2]

y = [1,2]

🔹 Step 3: Execute x = x + [3]

x = x + [3]

⚠️ Very important difference 😈

This does NOT modify existing list.

Instead:

x + [3]

creates a NEW list.

So:

[1,2] + [3]

→ [1,2,3]

Then:

x = [1,2,3]

Now x points to NEW list.

Visual:

y ───> [1,2]

x ───> [1,2,3]

🔹 Step 4: Execute print(y)

print(y)

y still points to OLD list:

[1,2]

So output becomes:

[1, 2]

🔥 Final Output

[1, 2]

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