192 – Break from nested loops

Breaking out of nested for loops requires auxiliary variables and conditional statements:

done = False
for n in range(1, len(switches) + 1):
    for group in combinations(switches, n):
        state = simplify(group)
        if state == target:
            print("found!")
            done = True
            break
    if done:
        break

You need to use the Boolean flag done and an extra if done statement to be able to break out of the two loops once you find the value of state for which state == target.

To improve this code, you can refactor the looping logic into a generator:

def groups_of_switches(switches):
    for n in range(1, len(switches) + 1):
        for group in combinations(switches, n):
            yield group

The generator should contain only the loops and no other logic. By extracting the loops into a generator, you can refactor the original code so it’s flatter:

for group in groups_of_switches(switches):
    state = simplify(group)
    if state == target:
        print("found!")
        break

The flatter code is easier to reason about and it’s easier to break out of this loop because it’s no longer nested.