async.py 文件源码

def defer(f=None, predicate=None):
    """
    Schedule a function to run in a cpu_bound thread, returns a AsyncFuture
    Optional predicate parameter to determine if the function should be dispatched
    """
    if f is None:
        def p_wrap(f):
            return defer(f, predicate)
        return p_wrap
    else:
        def f_wrap(f, *args, **kwargs):
            if CPUThread._thread is None:
                CPUThread._thread = CPUThread()
            return CPUThread._thread.apply(f, args, kwargs)

        def wrapper(*args, **kwargs):
            a = AsyncFuture(None, None)
            # TODO: unit test this
            if (predicate is not None and not predicate) or utils.in_cpubound_thread():
                v = f(*args, **kwargs)
                a._value = v
            else:
                g = Greenlet(f_wrap, f, *args, **kwargs)
                g.start()
                a._future = g
            return a
        return wrapper