Python Coding Challenge - Question with Answer (ID -021225)

 

Step-by-Step Execution

Initial list

arr = [1, 2, 3]

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✅ 1st Iteration

i = 1
arr.remove(1)

List becomes:

[2, 3]

Now Python moves to the next index (index 1).

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✅ 2nd Iteration

Now the list is:

[2, 3]

Index 1 has:

i = 3

So:

arr.remove(3)

List becomes:

[2]

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✅ Loop Ends

There is no next element to continue.

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✅ Final Output

[2]

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Why This Happens (Important Concept)

• You are modifying the list while looping over it

• When an element is removed:

  • The list shifts to the left

  • The loop skips elements

• This causes unexpected results

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✅ Correct Way to Remove All Elements

✔️ Option 1: Loop on a copy

for i in arr[:]: 
    arr.remove(i)

✔️ Option 2: Use clear()

arr.clear()

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Key Interview Point

❌ Never modify a list while iterating over it directly.

Mastering Pandas with Python