如何阻止和等待基于回调的异步，Python函数调用

Question

我有一个Python脚本会产生许多异步请求。 我正在使用的API进行回调。

主函数调用run，我希望它阻止执行，直到所有请求都返回。

我可以在Python 2.7中使用什么来实现这一目标？

def run():
    for request in requests:
        client.send_request(request, callback)

def callback(error, response):
    # handle response
    pass

def main():
    run()

    # I want to block here

Answer 1

我发现最简单，侵入性最小的方法是使用threading.Event ， 在2.7中可用 。

import threading
import functools

def run():
    events = []
    for request in requests:
        event = threading.Event()
        callback_with_event = functools.partial(callback, event)
        client.send_request(request, callback_with_event)
        events.append(event)

    return events

def callback(event, error, response):
    # handle response
    event.set()

def wait_for_events(events):
    for event in events:
        event.wait()

def main():
    events = run()
    wait_for_events(events)