from oslo_service import loopingcall

def _wait_for_image_state():
    global num
    num = 0
    def _wait_for_state():
        global num
        print num
        num = num + 1
        if num == 10:
            raise loopingcall.LoopingCallDone()

    timer = loopingcall.FixedIntervalLoopingCall(_wait_for_state)
    timer.start(interval=0.5).wait()

_wait_for_image_state()

[root@localhost ~]# python loopingcall.py 
0
1
2
3
4
5
6
7
8
9