Django視圖函數(shù)執(zhí)行，不在主線程中，直接loop = asyncio.new_event_loop() # 不能loop = asyncio.get_event_loop() 會觸發(fā)RuntimeError: There is no current event loop in thread

因為asyncio程序中的每個線程都有自己的事件循環(huán)，但它只會在主線程中為你自動創(chuàng)建一個事件循環(huán)。所以如果你asyncio.get_event_loop在主線程中調用一次，它將自動創(chuàng)建一個循環(huán)對象并將其設置為默認值，但是如果你在一個子線程中再次調用它，你會得到這個錯誤。相反，您需要在線程啟動時顯式創(chuàng)建/設置事件循環(huán)：

loop = asyncio.new_event_loop()asyncio.set_event_loop(loop)

在Django單個視圖中使用asyncio實例代碼如下（有多個IO任務時）

from django.views import Viewimport asyncioimport timefrom django.http import JsonResponse class TestAsyncioView(View): def get(self, request, *args, **kwargs): ''' 利用asyncio和async await關鍵字（python3.5之前使用yield）實現(xiàn)協(xié)程 ''' self.id = 5 start_time = time.time() ’’’ # 同步執(zhí)行 # results = [self.io_task1(self.id), # self.io_task2(self.id), # self.io_task2(self.id)] ’’’ loop = asyncio.new_event_loop() # 或 loop = asyncio.SelectorEventLoop() asyncio.set_event_loop(loop) self.loop = loop works = [ asyncio.ensure_future(self.io_task3(5)), asyncio.ensure_future(self.io_task3(5)), asyncio.ensure_future(self.io_task3(5)), asyncio.ensure_future(self.io_task3(5)), asyncio.ensure_future(self.io_task3(5)), ] try: results = loop.run_until_complete(asyncio.gather(*works)) # 兩種寫法 # results = loop.run_until_complete(self.gather_tasks()) finally: loop.close() end_time = time.time() return JsonResponse({’results’: results, ’cost_time’: (end_time - start_time)}) async def gather_tasks(self): tasks = ( self.make_future(self.io_task1, self.id), self.make_future(self.io_task2, self.id), self.make_future(self.io_task2, self.id), self.make_future(self.io_task1, self.id), self.make_future(self.io_task2, self.id), self.make_future(self.io_task2, self.id), ) results = await asyncio.gather(*tasks) return results async def make_future(self, func, *args): future = self.loop.run_in_executor(None, func, *args) response = await future return response def io_task1(self, sleep_time): time.sleep(sleep_time) return 66 def io_task2(self, sleep_time): time.sleep(sleep_time) return 77 async def io_task3(self, sleep_time): # await asyncio.sleep(sleep_time) s = await self.do(sleep_time) return s async def do(self, sleep_time): await asyncio.sleep(sleep_time) return 66

在Django單個視圖中使用ThreadPoolExecutor實例代碼如下（有多個IO任務時）

from django.views import Viewimport timefrom concurrent.futures import ThreadPoolExecutor, as_completed class TestThreadView(View): def get(self, request, *args, **kargs): start_time = time.time() future_set = set() tasks = (self.io_task1, self.io_task2, self.io_task2, self.io_task1, self.io_task2, self.io_task2) with ThreadPoolExecutor(len(tasks)) as executor: for task in tasks:future = executor.submit(task, 5)future_set.add(future) for future in as_completed(future_set): error = future.exception() if error is not None:raise error results = self.get_results(future_set) end_time = time.time() return JsonResponse({’results’: results, ’cost_time’: (end_time - start_time)}) def get_results(self, future_set): results = [] for future in future_set: results.append(future.result()) return results def io_task1(self, sleep_time): time.sleep(sleep_time) return 66 def io_task2(self, sleep_time): time.sleep(sleep_time) return 77

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