else — Intermediate Playground

Catch-all branch when preceding if/elif conditions are all false

Python Playground

# for/else: check if a number is prime
def is_prime(n):
    if n < 2:
        return False
    for i in range(2, int(n**0.5) + 1):
        if n % i == 0:
            return False  # could use break + else here too
    return True

# Using for/else pattern
for n in [17, 18, 19, 20]:
    for i in range(2, n):
        if n % i == 0:
            print(f"{n} = {i} x {n//i}")
            break
    else:
        print(f"{n} is prime")

Output

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Loop else is unusual: it runs when the loop finishes normally (without break). Think of it as 'nobreak' — it runs if break was never hit.

Challenge

Try modifying the code above to explore different behaviors. Can you extend the example to handle a new use case?

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