Python Coding Challange - Question with Answer (01231025)

 

Step-by-step execution:

Initial array:
arr = [1, 2, 3]

The for loop iterates over the list, but note — the list is changing during iteration.

---

Iteration 1:

i = 1

• arr.remove(1) → removes the first occurrence of 1

• Now arr = [2, 3]

But — Python’s for loop moves to the next index (index 1)
👉 So now it skips checking the element at index 0 (which became 2 after removal).

---

Iteration 2:

• Next element (at index 1) is 3

• arr.remove(3) removes 3

• Now arr = [2]

---

Loop ends (because Python has already iterated through what it thinks were 3 elements).

---

✅ Final Output:

[2]

---

🔹 Why does this happen?

Because modifying a list while looping over it confuses the iterator —
the loop skips elements since the list shrinks and indexes shift.

---

💡 Best Practice:

Never modify a list while iterating over it.
Instead, use a copy:

arr = [1, 2, 3]
for i in arr[:]:
    arr.remove(i)
print(arr) # Output: []

---

So the correct answer is ✅ [2]

Python Projects for Real-World Applications