Lesson 3.2 — Prompting for Coding Help

💬 Prompt

Write a Python function that removes duplicate values from a list while preserving the original order. Include a docstring and one usage example.

🐍 Python — Sample AI Response

def remove_duplicates(items):
    """Return a new list with duplicates removed, preserving order."""
    seen = set()
    result = []
    for item in items:
        if item not in seen:
            seen.add(item)
            result.append(item)
    return result

# Example usage:
# remove_duplicates([1, 2, 2, 3, 1]) -> [1, 2, 3]

✅ How It Works

The function walks through the list once, keeping track of values already seen in a set for fast lookup, and only adds a value to the result the first time it appears — which preserves the original order. Calling remove_duplicates([1, 2, 2, 3, 1]) returns [1, 2, 3].

Practical Tip

Ask the AI to rewrite the same function in a different language you’re curious about, like JavaScript, using the exact same prompt structure. Notice how little you have to change to get an equally solid result.

Key Takeaway

Naming the language, the exact rule, and the deliverable format leaves little room for the model to guess wrong.