Eventually I found an answer in this thread. The method I was looking for is run_in_executor. This allows a synchronous function to be run asynchronously without blocking an event loop. In the sleep example I posted above, it might look like this: import asyncio from time import sleep async def sleep_async(loop, delay): # None uses … Read more
asyncio.run is a Python 3.7 addition. In 3.5-3.6, your example is roughly equivalent to: import asyncio futures = […] loop = asyncio.get_event_loop() loop.run_until_complete(asyncio.wait(futures))
The equivalent would be using asyncio.gather: import asyncio async def bar(i): print(‘started’, i) await asyncio.sleep(1) print(‘finished’, i) async def main(): await asyncio.gather(*[bar(i) for i in range(10)]) loop = asyncio.get_event_loop() loop.run_until_complete(main()) loop.close() Why doesn’t my approach work? Because when you await each item in seq, you block that coroutine. So in essence, you have synchronous code … Read more
In your def demo_async(urls), try to replace: loop = asyncio.get_event_loop() with: loop = asyncio.new_event_loop() asyncio.set_event_loop(loop)
For Python versions below 3.5: import asyncio @asyncio.coroutine def periodic(): while True: print(‘periodic’) yield from asyncio.sleep(1) def stop(): task.cancel() loop = asyncio.get_event_loop() loop.call_later(5, stop) task = loop.create_task(periodic()) try: loop.run_until_complete(task) except asyncio.CancelledError: pass For Python 3.5 and above: import asyncio async def periodic(): while True: print(‘periodic’) await asyncio.sleep(1) def stop(): task.cancel() loop = asyncio.get_event_loop() loop.call_later(5, stop) … Read more
You aren’t seeing anything special because there’s nothing much asynchronous work in your code. However, the main difference is that time.sleep(5) is blocking, and asyncio.sleep(5) is non-blocking. When time.sleep(5) is called, it will block the entire execution of the script and it will be put on hold, just frozen, doing nothing. But when you call … Read more
If I’m not mistaken you’re searching for asyncio.Semaphore. Example of usage: import asyncio from random import randint async def download(code): wait_time = randint(1, 3) print(‘downloading {} will take {} second(s)’.format(code, wait_time)) await asyncio.sleep(wait_time) # I/O, context will switch to main function print(‘downloaded {}’.format(code)) sem = asyncio.Semaphore(3) async def safe_download(i): async with sem: # semaphore limits … Read more
Where I’m coming from: I’m the primary author of trio. I’m also one of the top contributors to curio (and wrote the article about it that you link to), and a Python core dev who’s been heavily involved in discussions about how to improve asyncio. In trio (and curio), one of the core design principles … Read more
The asyncio.run() documentation says: This function cannot be called when another asyncio event loop is running in the same thread. In your case, jupyter (IPython ≥ 7.0) is already running an event loop: You can now use async/await at the top level in the IPython terminal and in the notebook, it should — in most of the … Read more
Since Python 3.8 unittest comes with the IsolatedAsyncioTestCase function, designed for this purpose. from unittest import IsolatedAsyncioTestCase class Test(IsolatedAsyncioTestCase): async def test_functionality(self): result = await functionality() self.assertEqual(expected, result)