Lab · School of Computer Science & Technology

Lab 3 — Functions

⏱️ ~7 minutes · Use Python. Solutions in solutions.html.

Goal

Package logic into reusable functions that return values, then feed those values into decisions.

Tasks

1. Write a function is_even(n) that returns True if n is even, False otherwise. (Hint: n % 2 == 0 is already a boolean — you can return it directly.) Test it: print(is_even(4)) → True, print(is_even(7)) → False.

2. Write a function grade(score) that returns a letter:

   • "A" for 90+, "B" for 80–89, "C" for 70–79, otherwise "F". Test it with a few scores.

3. Call your functions together:

   print("Score 85 is even:", is_even(85), "and gets a", grade(85))

Stretch (optional)

• Add a parameter to grade with a default value, e.g. grade(score, passing=70), and return "PASS"/"FAIL".
• Demonstrate scope: create a variable inside grade and try to print it outside the function. What error do you get, and why?

What you're practicing

Defining functions, parameters vs. arguments, return values, and composing functions — the anatomy behind every library call you'll make in AI (model.fit(...), np.mean(...)).