Python coroutines

gistfile1.txt

def cr():
    state = False
    for i in range(100):
        new_state = None
        if state:
            new_state = (yield i)
        else:
            new_state = (yield "Off")
        if not (new_state is None):
            state = new_state

c = cr()
assert(c.next() == 'Off')
assert(c.next() == 'Off')
assert(c.send(True) == 2)
assert(c.next() == 3)
assert(c.next() == 4)
assert(c.send(False) == 'Off')
assert(c.next() == 'Off')