在Python中使异步调用同步

Question

使异步调用显示为同步的最佳方法是什么？例如,像这样的东西,但我如何协调调用线程和异步回复线程？在java中我可能会使用带有超时的CountdownLatch(),但我找不到Python的明确解决方案

def getDataFromAsyncSource():
    asyncService.subscribe(callback=functionToCallbackTo)
    # wait for data
    return dataReturned

def functionToCallbackTo(data):
    dataReturned = data

Answer 1

您可以使用一个模块

import concurrent.futures

查看这篇文章,了解示例代码和模块下载链接:Python中的并发任务执行

您可以在将来放置执行程序结果,然后获取它们,这是来自http://pypi.python.org的示例代码:

import concurrent.futures
import urllib.request

URLS = ['http://www.foxnews.com/',
    'http://www.cnn.com/',
    'http://europe.wsj.com/',
    'http://www.bbc.co.uk/',
    'http://some-made-up-domain.com/']

def load_url(url, timeout):
    return urllib.request.urlopen(url, timeout=timeout).read()

with concurrent.futures.ThreadPoolExecutor(max_workers=5) as executor:
    future_to_url = dict((executor.submit(load_url, url, 60), url)
                     for url in URLS)

    for future in concurrent.futures.as_completed(future_to_url):
        url = future_to_url[future]
        if future.exception() is not None:
            print('%r generated an exception: %s' % (url,future.exception()))
        else:
            print('%r page is %d bytes' % (url, len(future.result())))