python - 等到几个绿叶中的一个完成

Question

我有两个函数从两个不同的连接接收数据，我应该在从其中一个获得结果后关闭两个连接。

def first():
    gevent.sleep(randint(1, 100))  # i don't know how much time it will work
    return 'foo'

def second():
    gevent.sleep(randint(1, 100))  # i don't know how much time it will work
    return 'bar'

然后我生成每个函数:

lst = [gevent.spawn(first), gevent.spawn(second)]

gevent.joinall 阻塞当前的 greenlet，直到来自 lst 的两个 greenlet 都准备好了。

gevent.joinall(lst)  # wait much time
print lst[0].get(block=False)   # -> 'foo'
print lst[1].get(block=False)   # -> 'bar'

我想等到第一个或第二个 greenlet 准备就绪:

i_want_such_function(lst)  # returns after few seconds
print lst[0].get(block=False)  # -> 'foo' because this greenlet is ready
print lst[1].get(block=False)  # -> raised Timeout because this greenlet is not ready

我该怎么做？

Answer 1

您可以使用 gevent.event.Event(或 AsyncResult)和 Greenlet 的 link() 方法，如下所示:

...
ready = gevent.event.Event()
ready.clear()

def callback():
    ready.set()

lst = [gevent.spawn(first), gevent.spawn(second)]
for g in lst:
    g.link(callback)

ready.wait()
...