我几乎没有阻止功能foo
,bar
而且我无法更改这些功能(我无法控制某些内部库。与一个或多个网络服务进行对话)。我如何将其用作异步?例如。我不想做以下事情。
results = []
for inp in inps:
val = foo(inp)
result = bar(val)
results.append(result)
这样效率很低,因为我在等待foo
的第一个输入时可以调用bar
进行第二次输入。如何将它们包装起来以便它们可以与asyncio一起使用(即新的async
,await
语法)?
让我们假设这些功能是可重入的。也就是说,只有在前一个foo
正在处理时再次致电foo
。
更新
使用可重复使用的装饰器扩展答案。例如,点击here。
def run_in_executor(f):
@functools.wraps(f)
def inner(*args, **kwargs):
loop = asyncio.get_running_loop()
return loop.run_in_executor(None, functools.partial(f, *args, **kwargs))
return inner
答案 0 :(得分:14)
这里有两个问题:第一,如何异步运行阻塞代码,第二,如何并行运行异步代码(asyncio是单线程的,所以GIL仍然适用,所以它不是真正并发,但我离题了。)
可以使用asyncio.ensure_future创建并行任务,如文档here所述。
要运行同步代码,您需要run the blocking code in an executor。例如:
import concurrent.futures
import asyncio
import time
def blocking(delay):
time.sleep(delay)
print('Completed.')
async def non_blocking(loop, executor):
# Run three of the blocking tasks concurrently. asyncio.wait will
# automatically wrap these in Tasks. If you want explicit access
# to the tasks themselves, use asyncio.ensure_future, or add a
# "done, pending = asyncio.wait..." assignment
await asyncio.wait(
fs={
# Returns after delay=12 seconds
loop.run_in_executor(executor, blocking, 12),
# Returns after delay=14 seconds
loop.run_in_executor(executor, blocking, 14),
# Returns after delay=16 seconds
loop.run_in_executor(executor, blocking, 16)
},
return_when=asyncio.ALL_COMPLETED
)
loop = asyncio.get_event_loop()
executor = concurrent.futures.ThreadPoolExecutor(max_workers=5)
loop.run_until_complete(non_blocking(loop, executor))
如果您想使用for循环计划这些任务(如您的示例所示),您有几种不同的策略,但基本方法是使用for循环(或列表)计划任务理解等),用asyncio.wait等待它们,然后检索结果。例如:
done, pending = await asyncio.wait(
fs=[loop.run_in_executor(executor, blocking_foo, *args) for args in inps],
return_when=asyncio.ALL_COMPLETED
)
# Note that any errors raise during the above will be raised here; to
# handle errors you will need to call task.exception() and check if it
# is not None before calling task.result()
results = [task.result() for task in done]
答案 1 :(得分:0)
扩展接受的答案以实际解决相关问题。
注意:需要python 3.7 +
import functools
from urllib.request import urlopen
import asyncio
def legacy_blocking_function(): # You cannot change this function
r = urlopen("https://example.com")
return r.read().decode()
def run_in_executor(f):
@functools.wraps(f)
def inner(*args, **kwargs):
loop = asyncio.get_running_loop()
return loop.run_in_executor(None, lambda: f(*args, **kwargs))
return inner
@run_in_executor
def foo(arg): # Your wrapper for async use
resp = legacy_blocking_function()
return f"{arg}{len(resp)}"
@run_in_executor
def bar(arg): # Another wrapper
resp = legacy_blocking_function()
return f"{len(resp)}{arg}"
async def process_input(inp): # Modern async function (coroutine)
res = await foo(inp)
res = f"XXX{res}XXX"
return await bar(res)
async def main():
inputs = ["one", "two", "three"]
input_tasks = [asyncio.create_task(process_input(inp)) for inp in inputs]
print([await t for t in asyncio.as_completed(input_tasks)])
# This doesn't work as expected :(
# print([await t for t in asyncio.as_completed([process_input(inp) for inp in input_tasks])])
if __name__ == '__main__':
asyncio.run(main())
单击here获取此示例的最新版本并发送请求请求。
答案 2 :(得分:0)
import asyncio
from time import sleep
import logging
logging.basicConfig(
level=logging.DEBUG, format="%(asctime)s %(thread)s %(funcName)s %(message)s")
def long_task(t):
"""Simulate long IO bound task."""
logging.info("2. t: %s", t)
sleep(t)
logging.info("4. t: %s", t)
return t ** 2
async def main():
loop = asyncio.get_running_loop()
inputs = range(1, 5)
logging.info("1.")
futures = [loop.run_in_executor(None, long_task, i) for i in inputs]
logging.info("3.")
results = await asyncio.gather(*futures)
logging.info("5.")
for (i, result) in zip(inputs, results):
logging.info("6. Result: %s, %s", i, result)
if __name__ == "__main__":
asyncio.run(main())
输出:
2020-03-18 17:13:07,523 23964 main 1.
2020-03-18 17:13:07,524 5008 long_task 2. t: 1
2020-03-18 17:13:07,525 21232 long_task 2. t: 2
2020-03-18 17:13:07,525 22048 long_task 2. t: 3
2020-03-18 17:13:07,526 25588 long_task 2. t: 4
2020-03-18 17:13:07,526 23964 main 3.
2020-03-18 17:13:08,526 5008 long_task 4. t: 1
2020-03-18 17:13:09,526 21232 long_task 4. t: 2
2020-03-18 17:13:10,527 22048 long_task 4. t: 3
2020-03-18 17:13:11,527 25588 long_task 4. t: 4
2020-03-18 17:13:11,527 23964 main 5.
2020-03-18 17:13:11,528 23964 main 6. Result: 1, 1
2020-03-18 17:13:11,528 23964 main 6. Result: 2, 4
2020-03-18 17:13:11,529 23964 main 6. Result: 3, 9
2020-03-18 17:13:11,529 23964 main 6. Result: 4, 16