python asyncio-RuntimeError:未来未使用await

问题描述

我想使用带有collect()的信号量来限制api调用.我认为我必须使用create_task()，但是会遇到一个运行时错误:"RuntimeError:await未与将来一起使用".我该如何解决?

I want to use a semaphore with a gather() to limit api calls. I think I have to use create_task() but I obtain a runtime error: "RuntimeError: await wasn't used with future". How can I fix it?

代码如下:

import asyncio
# pip install git+https://github.com/sammchardy/python-binance.git@00dc9a978590e79d4aa02e6c75106a3632990e8d
from binance import AsyncClient


async def catch_up_aggtrades(client, symbols):
    tasks = asyncio.create_task(get_historical_aggtrades(client, symbol) for symbol in symbols)
    sem = asyncio.Semaphore(1)
    async with sem:
        await asyncio.gather(*tasks)


async def get_historical_aggtrades(client, symbol):
    async for trade in client.aggregate_trade_iter(symbol, '1 day ago UTC'):
        print(f"symbol {symbol}")


async def main():
    client = await AsyncClient.create()
    symbols = ['BTCUSDT', 'ETHUSDT', 'BNBUSDT']
    await catch_up_aggtrades(client, symbols)


if __name__ == "__main__":
    loop = asyncio.get_event_loop()
    loop.run_until_complete(main())

推荐答案

限制资源使用的方法实际上是一个非常简单的概念.这类似于计算免费停车场.(汽车进入时为-1，离开汽车时为+1).当计数器降为零时，等待的汽车队列开始建立.

A sempahore limiting a resource usage is actually a very simple concept. It is similar to counting free parking lots. (-1 when a car enters, +1 when it leaves). When the counter drops to zero, a queue of waiting cars starts to build.

这意味着:

• 每个资源一个信号量
• 初始值=并发资源用户的上限
• 每种资源的使用由与sem异步进行保护:

现有代码:

sem = asyncio.Semaphore(1)
async with sem:
    await asyncio.gather(*tasks)

将 asyncio.gather 的使用限制为一次只能收集1个任务.它不限制任务，仅限制任务的收集.由于 gather 始终只被调用一次，因此该信号量不会改变任何内容.

limits the use of asyncio.gather to 1 task gathering at a time. It does not limit the tasks, just their gathering. Since the gather is called just once anyway, the semaphore does not change anything.

您的程序可能更改为(包括注释中解决的问题):

Your program might be changed to (including the issue resolved in comments):

LIMIT = 1

async def catch_up_aggtrades(client, symbols):
    sem = asyncio.Semaphore(LIMIT)
    tasks = [asyncio.create_task(get_historical_aggtrades(client, symbol, sem)) for symbol in symbols]
    await asyncio.gather(*tasks)

async def get_historical_aggtrades(client, symbol, sem):
    async with sem:
        async for trade in client.aggregate_trade_iter(symbol, '1 day ago UTC'):
            print(f"symbol {symbol}")

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