Lesson 3 of 40 Foundations Beginner ⏱ 25 min

Control Flow — if, for, while, match

Control program flow with if/elif/else, Python's structural pattern matching (match/case), for loops with enumerate, while loops, and comprehension shortcuts.

Part 1: if / elif / else

score = 85
if score >= 90:
    grade = "A"
elif score >= 80:
    grade = "B"
else:
    grade = "C or below"

# Ternary (conditional expression)
status = "pass" if score >= 50 else "fail"

Part 2: match / case — Structural Pattern Matching

# Python 3.10+ match statement
def handle_command(command):
    match command:
        case "quit" | "exit":
            return "Goodbye!"
        case {"action": action, "target": target}:
            return f"Do {action} on {target}"
        case [first, *rest]:
            return f"List starting with {first}"
        case _:
            return "Unknown"

Part 3: for loops with enumerate & zip

fruits = ["apple", "banana", "cherry"]

# enumerate gives index + value
for i, fruit in enumerate(fruits, start=1):
    print(f"{i}. {fruit}")

# zip — iterate multiple lists together
names = ["Alice", "Bob"]
scores = [95, 82]
for name, score in zip(names, scores):
    print(f"{name}: {score}")

# range
for i in range(0, 10, 2): # 0,2,4,6,8
    print(i)

Part 4: while, break, continue & else

# while with else (runs if loop wasn't broken)
n = 1
while n <= 100:
    if n % 7 == 0:
        print(f"Found: {n}")
        break
    n += 1
else:
    print("No multiple of 7 found")