break and continue

Leaving early and skipping ahead

Two keywords change how a loop flows:

• break stops the loop immediately and carries on after it
• continue abandons this pass and jumps to the next one

for n in numbers:
    if n < 0:
        continue      # ignore negatives
    if n > 100:
        break         # stop entirely
    print(n)

break is the natural way to write a search: as soon as you have found what you are looking for, there is no reason to keep going.

Your turn: write first_negative(numbers) returning the first negative number in the list, or None if there are none. Stop looking as soon as you find one.

Skipping with continue

continue keeps the interesting case unindented, which makes a loop much easier to read than wrapping the whole body in an if.

for line in lines:
    if not line:
        continue
    process(line)

Your turn: write sum_positive(numbers) adding up only the numbers greater than zero, skipping the rest with continue.