Loops

for loops

A for loop iterates over anything iterable — a list, string, range, dict, or file. range(n) generates 0, 1, ..., n-1; range(a, b) generates a, ..., b-1.

for i in range(5):
    print(i)   # 0 1 2 3 4

videos = ["Intro", "Variables", "Loops"]
for video in videos:
    print("Now playing:", video)

for index, video in enumerate(videos):
    print(index, "->", video)   # enumerate() gives you both index and value

while loops

Repeats while a condition stays true — use it when you don't know the number of iterations upfront (waiting for user input, polling, game loops).

subscribers = 0
target = 5
while subscribers < target:
    subscribers += 1
    print(f"Gained subscriber #{subscribers}")
print("Reached the target!")

A while True: loop repeats forever until something inside explicitly breaks out of it — a very common pattern for "keep asking until valid input."

break, continue, and the loop's else

break exits the loop entirely; continue skips the rest of the current iteration and moves to the next one. A loop's else block runs only if the loop finished without hitting break — a lesser-known but genuinely useful feature for "search and report if not found" patterns.

videos = ["Intro", "Variables", "Loops", "Functions"]
target = "Functions"

for video in videos:
    if video == target:
        print("Found it!")
        break
else:
    print("Not in the playlist")

Classic drill: FizzBuzz

for i in range(1, 16):
    if i % 15 == 0:
        print("FizzBuzz")
    elif i % 3 == 0:
        print("Fizz")
    elif i % 5 == 0:
        print("Buzz")
    else:
        print(i)