circuits framework recursive events

import time
from circuits import Component, Debugger, Event

class factorial(Event): pass

class App(Component):
    def factorial(self, n):
        time.sleep(1)
        if n > 1:
            nn = yield self.call(factorial(n-1))
            yield n * nn.value
        else:
            yield 1

    def started(self, *args):
        rv = yield self.call(factorial(5))
        print(rv.value)
        self.stop()

(App() + Debugger()).run()