Python Coding Challenge - Question with Answer (ID -120526)

 

Explanation:

🔹 Step 1: Create Tuple

x = ([1,2],)

x is a tuple

Tuple contains one list:

[1,2]

👉 Current value:

([1, 2],)

⚠️ Important:

Tuple itself is immutable ❌

But list inside tuple is mutable ✅

🔹 Step 2: Execute x[0] += [3]

x[0] += [3]

This line is VERY tricky 😈

Python internally performs TWO operations.

⚡ Step 2.1: Modify the Inner List

[1,2] += [3]

This updates list IN-PLACE.

👉 List becomes:

[1,2,3]

So internally tuple now looks like:

([1,2,3],)

⚡ Step 2.2: Python Tries Reassignment

After modifying list, Python internally tries:

x[0] = [1,2,3]

BUT ❗

Tuple does NOT allow item assignment

Tuple is immutable

So Python raises:

TypeError

🔹 Step 3: Error Occurs Before Print

print(x)

This line never executes because error already happened.

⚡ Important Twist 😈

Even though error occurs:

👉 List WAS modified successfully before error

Internally:

x = ([1,2,3],)

BUT print never runs.

🔥 Final Result

TypeError