Solutions

Lab Solutions

Reference solutions in Python. There's always more than one correct answer — if a student's version produces the right output and reads clearly, it's right. Teaching notes are in bold.

Lab 1 — Variables & Data Types

# 1. Variables of each core type
name = "Ada"
age = 25
gpa = 3.8
is_enrolled = True

# 2. Print a sentence (f-string is the readable, modern way)
print(f"{name} is {age} years old, GPA {gpa}, enrolled: {is_enrolled}")

# 3. The bug
age_text = "25"
# print(age_text + 5)   # TypeError: can only concatenate str (not "int") to str

# 4. The fix — convert text to a number first
print(int(age_text) + 5)   # 30

Teaching note: Task 3 is the point of the whole lab. "25" looks like a number but is text; Python refuses to add text and a number. int("25") converts it. This is exactly what happens when data arrives from a CSV/form as strings — converting types correctly is data cleaning.

Stretch:

print(type(name), type(age), type(gpa), type(is_enrolled))
# <class 'str'> <class 'int'> <class 'float'> <class 'bool'>
print(0.1 + 0.2)   # 0.30000000000000004  -> floats are approximate; never compare with ==

Lab 2 — Control Flow (mini FizzBuzz)

Final version (steps 1–3 combined):

for n in range(1, 21):
    if n % 3 == 0 and n % 5 == 0:   # check BOTH first
        print("FizzBuzz")
    elif n % 3 == 0:
        print("Fizz")
    elif n % 5 == 0:
        print("Buzz")
    else:
        print(n)

Teaching note: Why check "both" first? Because 15 is a multiple of 3 and 5. If you tested n % 3 == 0 first, 15 would print "Fizz" and never reach the FizzBuzz case. Order of conditions is a real source of bugs — the most specific case goes first.

Stretch — while version:

n = 1
while n <= 20:
    # ... same if/elif/else ...
    n += 1   # <- forget this line and you get an INFINITE loop

Lab 3 — Functions

def is_even(n):
    return n % 2 == 0          # the comparison is already a boolean

def grade(score):
    if score >= 90:
        return "A"
    elif score >= 80:
        return "B"
    elif score >= 70:
        return "C"
    else:
        return "F"

print(is_even(4))    # True
print(is_even(7))    # False
print("Score 85 is even:", is_even(85), "and gets a", grade(85))
# Score 85 is even: False and gets a B

Teaching note: return n % 2 == 0 surprises beginners who expect an if/else. Stress that a comparison is a boolean, so you can return it directly. Note how grade(85)'s return value flows straight into print — functions composing is the whole game.

Stretch — default parameter & scope:

def grade(score, passing=70):
    return "PASS" if score >= passing else "FAIL"

def grade2(score):
    letter = "A"            # local variable
    return letter
# print(letter)  # NameError: 'letter' is not defined  -> it only exists INSIDE the function (scope)

Lab 4 — Capstone: Tiny Gradebook

def grade(score):
    if score >= 90: return "A"
    elif score >= 80: return "B"
    elif score >= 70: return "C"
    else: return "F"

students = [
    {"name": "Ada",   "score": 92},
    {"name": "Linus", "score": 78},
    {"name": "Grace", "score": 85},
    {"name": "Alan",  "score": 64},
]

# 2. Per-student report
for s in students:
    print(f"{s['name']:<6} | {s['score']} | {grade(s['score'])}")

# 3. Class average
scores = [s["score"] for s in students]      # a list comprehension — pull out every score
avg = sum(scores) / len(scores)
print(f"Class average: {avg:.1f}")           # 79.8

# 4. How many passed
passed = 0
for s in students:
    if s["score"] >= 70:
        passed += 1
print(f"Passed: {passed} / {len(students)}")  # 3 / 4

Output:

Ada    | 92 | A
Linus  | 78 | C
Grace  | 85 | B
Alan   | 64 | F
Class average: 79.8
Passed: 3 / 4

Stretch:

top = students[0]
for s in students:
    if s["score"] > top["score"]:
        top = s
print(f"Top student: {top['name']} ({top['score']})")   # Ada (92)

Teaching note: Narrate how every concept from the day appears here:

list of dicts = a dataset (rows of records),
for loop = process each row,
grade() function = reusable logic,
if inside the count = a decision,
sum/len + division = type-aware math,
f-strings with :<6 / :.1f = formatting output.

Swap students for rows read from a real CSV and they've written their first data pipeline — exactly the shape of practical AI/data work.