async.py 文件源码

def callback_when_complete(futures, callback):
    """
    Calls *callback* after all *futures* (list) have completed running.
    """
    counter = count(1)
    io_loop = IOLoop.current()
    results = []
    def add_one(f):
        c = counter.next()
        results.append(f.result())
        if c >= len(futures):
            return callback(results)
    for future in futures:
        io_loop.add_future(future, add_one)