Python Coding Challenge - Question with Answer (ID -090226)

 

Step-by-Step Explanation

Step 1 — Original List

data = [100, 200, 300]

A list with three numbers.

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Step 2 — Loop Starts

for i in data:

i takes copy of each value, not the actual list element.

Iterations:

• First → i = 100

• Second → i = 200

• Third → i = 300

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Step 3 — Modify i

i += 50

This changes only the temporary variable i, not the list.

So internally:

• 100 → 150 (temporary)

• 200 → 250 (temporary)

• 300 → 350 (temporary)

But data list is unchanged.

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Step 4 — Print List

print(data)

Since the original list was never modified:

[100, 200, 300]

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Important Concept (Interview Question)

Changing loop variable does NOT change list elements.

Because:

• i is a separate variable

• It does not point back to list index

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How to Actually Modify the List

Method 1 — Using Index

data = [100, 200, 300]

for i in range(len(data)):
    data[i] += 50
print(data)

Output:

[150, 250, 350]

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One-Line Pythonic Way

data = [100, 200, 300]
data = [i + 50 for i in data]

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Golden Rule (Very Important)

Loop variable changes value
List element stays same
Unless you use index.

Python Functions in Depth — Writing Clean, Reusable, and Powerful Code