Conditionals & Logic

Making decisions in code

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⏳ Loading Python... (first load takes ~10 seconds)

📖 Concept Recap

if/elif/else lets your code branch based on conditions.

Comparison operators: == != > < >= <=
Logical operators: and or not
Critical: = assigns a value, == compares two values.
Truthy/falsy: 0, empty string, empty list, and None are all falsy.

Python evaluates conditions top-to-bottom and stops at the first True branch. Order matters!

👀 Worked Example

A temperature classifier using nested conditions:

def classify_temperature(temp): if temp < 0: return "Freezing" elif temp < 10: return "Very Cold" elif temp < 20: return "Cool" elif temp < 30: return "Warm" else: return "Hot" temps = [-5, 5, 15, 25, 35] for t in temps: print(f"{t}°C → {classify_temperature(t)}")

✏️ Guided

Exercise 1 — Grade Classifier

Complete the grade classifier by filling in the threshold values. Standard scale: A=90+, B=80+, C=70+, D=60+, F=below 60.

def get_letter_grade(score):
    if score >= 90:
        return "A"
    elif score >= ___:   # fill in the B threshold
        return "B"
    elif score >= ___:   # fill in the C threshold
        return "C"
    elif score >= ___:   # fill in the D threshold
        return "D"
    else:
        return "F"

scores = [95, 83, 71, 65, 42]
for s in scores:
    print(f"Score {s}: {get_letter_grade(s)}")

Output will appear here...

💡 Hint: B starts at 80, C at 70, D at 60. Expected output: A, B, C, D, F.

💪 Independent

Exercise 2 — Voter Eligibility

Write a function can_vote(age, is_citizen) that returns True only if age ≥ 18 AND is_citizen is True. Test it with four different combinations:

age=20, is_citizen=True
age=16, is_citizen=True
age=25, is_citizen=False
age=17, is_citizen=False

# Your code here

Output will appear here...

💡 Hint: Use and to combine two conditions: return age >= 18 and is_citizen

🔥 Challenge

Exercise 3 — FizzBuzz

Write a FizzBuzz function. For numbers 1 through 30:

Print "FizzBuzz" if divisible by both 3 and 5
Print "Fizz" if divisible by 3 only
Print "Buzz" if divisible by 5 only
Otherwise print the number

Important: The FizzBuzz check must come first. Why?

# Write your FizzBuzz solution here

Output will appear here...

💡 Hint: Use the modulo operator % to check divisibility. 15 % 3 == 0 is True. Check FizzBuzz (divisible by 15) BEFORE checking Fizz or Buzz individually.

🏆 Mini Project

Mini Project — Grade Report Calculator

Build a complete grade calculator. Given the scores below, calculate and print:

The average score
The letter grade for the average
Whether the student is on honor roll (average ≥ 90)
The highest and lowest scores
A formatted grade report

scores = [88, 92, 79, 95, 84, 91]
# Calculate and print a complete grade report

Output will appear here...

💡 Hint: Use sum(scores) / len(scores) for the average, max(scores) and min(scores) for highest/lowest. Reuse your get_letter_grade() function from Exercise 1!

✅ Lab 2 Complete!

You’ve mastered conditionals, comparison operators, logical operators, and built a complete grade calculator. Decision-making is at the heart of every useful program.

Continue to Lab 3: Loops & Iteration →

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