breakable.py

from contextlib import contextmanager

@contextmanager
def breakable():
    class Break(Exception): pass
    def breaker(): raise Break
    try:
        yield breaker
    except Break:
        pass


for outer in range(5):
    with breakable() as brk:
        for middle in range(5):
            for inner in range(10):
                print(outer, middle, inner)
                if middle == 1 and inner == 5:
                    brk()
            print(f"end middle loop #{middle}")
    print(f"end outer loop #{outer}")
print("done")