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Django視圖函數執行，不在主線程中，直接loop = asyncio.new_event_loop()
# 不能loop = asyncio.get_event_loop() 會觸發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，但它只會在主線程中為你自動創建一個事件循環。所以如果你asyncio.get_event_loop在主線程中調用一次，它將自動創建一個循環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建/設置事件循環：
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 View
import asyncio
import time
from 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）實現協程
"""
self.id = 5
start_time = time.time()
'''
# 同步執行
# 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 View
import time
from 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
以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持億速云。
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