def a(): print "a"
def b(): print "b"
def c(): print "c"

def pouet():
    try:
        pouet.func[pouet.index] ()
    except AttributeError:
        pouet.index = 0
        pouet.func = (a, b, c)
        pouet.func[pouet.index] ()
    pouet.index = (pouet.index + 1) % 3

pouet()
pouet()
pouet()
pouet()