Flask asyncio aiohttp - RuntimeError：线程'Thread-2'

Question

最近一直在阅读有关 python 并发的内容 realpython - python concurrency我的主要关注asyncio点是相当新的。执行异步活动的代码块使用asyncio并aiohttp在直接运行时运行良好。但是，当我将代码添加到我的烧瓶蓝图时，它会引发此错误：RuntimeError: There is no current event loop in thread 'Thread-2'出于演示目的，我制作了一个演示烧瓶应用程序。万一有人想测试一下。main.pyfrom flask import Flaskfrom my_blueprint import my_blueprint#Define flask appapp = Flask(__name__)#load blueprintsapp.register_blueprint(my_blueprint,url_prefix='/demo')#start flaskif __name__ == '__main__':    app.run(debug=True)my_blueprint.pyfrom flask import Blueprint,request, jsonify,abort,make_responsefrom flask import make_responseimport asyncioimport timeimport aiohttpmy_blueprint = Blueprint('my_blueprint', __name__)@my_blueprint.route('/',methods=['GET'])def home():    #code block    async def download_site(session, url):        async with session.get(url) as response:            print("Read {0} from {1}".format(response.content_length, url))    async def download_all_sites(sites):        async with aiohttp.ClientSession() as session:            tasks = []            for url in sites:                task = asyncio.ensure_future(download_site(session, url))                tasks.append(task)            await asyncio.gather(*tasks, return_exceptions=True)    sites = ["https://www.jython.org","http://olympus.realpython.org/dice"]*20    start_time = time.time()    asyncio.get_event_loop().run_until_complete(download_all_sites(sites))    duration = time.time() - start_time    return jsonify({"status":f"Downloaded {len(sites)} sites in {duration} seconds"})    #end of code block

Answer 1

编辑：看起来你的代码是正确的。我习惯写不同的。但是您可能正在运行 Windows 和 Python 3.8。这只是改变了 Windows 上 python 3.8 中的默认事件循环策略，而且它很容易出错。您可以改回旧的事件循环策略：

改变：

asyncio.get_event_loop().run_until_complete(download_all_sites(sites))

进入：

asyncio.set_event_loop(asyncio.SelectorEventLoop())

asyncio.get_event_loop().run_until_complete(download_all_sites(sites))