Python aiohttp : cancel async execution on met condition

Question

我为 CTF 游戏编写了一个异步暴力破解脚本，如下所示

async def bound_fetch(sem, session, answer):
    #  generating url, headers and json ...
    async with sem, session.post(url=url, json=json, headers=headers) as response:
        if response.status == 200:
            print('Right answer found: %s' % json['answer'])


async def run(words):
    tasks = []
    sem = asyncio.Semaphore(3)
    async with aiohttp.ClientSession() as session:
        for word in words:
            task = asyncio.create_task(bound_fetch(sem=sem, session=session, answer=''.join(word)))
            tasks.append(task)
        print("Generated %d possible answers. Checking %s" % (len(tasks), base_url))
        await asyncio.gather(*tasks)


if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    future = asyncio.ensure_future(run(possible_answers))
    loop.run_until_complete(future)

我的引用是本教程:https://pawelmhm.github.io/asyncio/python/aiohttp/2016/04/22/asyncio-aiohttp.html

我想知道这是否是在 aiohttp 中执行此操作的正确方法，或者我是否使事情变得太复杂(因为我不需要处理所有响应，只需知道哪个响应的状态为 200)？当满足条件(状态代码)时如何取消处理？

Answer 1

I was wondering if this is the right way to do it in aiohttp

您的代码相本地道。在顶层，您可以省略 asyncio.ensure_future 并简单地调用 asyncio.run(run(possible_answers))。

How do I cancel the processing when the condition (status code) is met?

您可以使用事件或 future 对象并等待它，而不是使用gather。您可能知道，运行协程不需要 gather(它们按照 create_task 的计划立即运行)，其明确目的就是等待所有协程完成。基于事件的同步可能如下所示:

async def bound_fetch(sem, session, answer, done):
    #  generating url, headers and json ...
    async with sem, session.post(url=url, json=json, headers=headers) as response:
        if response.status == 200:
            done.set()
            done.run_answer = json['answer']

async def run(words):
    sem = asyncio.Semaphore(3)
    done = asyncio.Event()
    async with aiohttp.ClientSession() as session:
        tasks = []
        for word in words:
            tasks.append(asyncio.create_task(bound_fetch(
                sem=sem, session=session, answer=''.join(word), done=done)))
        print("Generated %d possible answers. Checking %s" % (len(words), base_url))
        await done.wait()
        print('Right answer found: %s' % done.run_answer)
        for t in tasks:
            t.cancel()