Python asyncio error

Question

I tried to run the following program in Python 3.6.4

import asyncio
import concurrent.futures
import requests

async def main():

    with concurrent.futures.ThreadPoolExecutor(max_workers=20) as executor:

        loop = asyncio.get_event_loop()
        futures = [
            loop.run_in_executor(
                executor, 
                requests.get, 
                'http://example.org/'
            )
            for i in range(20)
        ]
        for response in await asyncio.gather(*futures):
            pass


loop = asyncio.get_event_loop()
loop.run_until_complete(main())

However, I got an error, saying that RuntimeError: This event loop is already running.

Here is the complete error message:

Traceback (most recent call last):

  File "<ipython-input-1-28cf105e6739>", line 1, in <module>
    runfile('C:/asyncio_test.py', wdir='C:/')

  File "c:\program files\python36\lib\site-packages\spyder\utils\site\sitecustomize.py", line 705, in runfile
    execfile(filename, namespace)

  File "c:\program files\python36\lib\site-packages\spyder\utils\site\sitecustomize.py", line 102, in execfile
    exec(compile(f.read(), filename, 'exec'), namespace)

  File "C:/asyncio_test.py", line 30, in <module>
    loop.run_until_complete(main())

  File "c:\program files\python36\lib\asyncio\base_events.py", line 454, in run_until_complete
    self.run_forever()

  File "c:\program files\python36\lib\asyncio\base_events.py", line 408, in run_forever
    raise RuntimeError('This event loop is already running')

RuntimeError: This event loop is already running

I then tried to run the program in Ubuntu 16.10

File "asyncio_test.py", line 18
    for response in await asyncio.gather(*futures):
                                ^
SyntaxError: invalid syntax

How to solve the problem?

Thank you very much.

Your code does not seem to be run directly. How do you start it? — Klaus D.
– Klaus D., Commented Apr 12, 2018 at 4:19

Richard Rublev · Accepted Answer · 2018-04-12 04:21:20Z

1

I can run your code on Ubuntu 16.04 without any problems.I think this is Windows signal handlers problem.Windows does not have signals and resolves if your code should exit in a different manner for console and GUi programs .Read more console control handdlers

answered Apr 12, 2018 at 4:21

Richard Rublev

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5 Comments

Chan Over a year ago

Thank you, Richard. How to modify the program to run in Windows?

Richard Rublev Over a year ago

I do not know,I have not worked with Windows 3,4 years.

Chan Over a year ago

I also tried to run the program in Ubuntu but there was an error. Please refer to the last part of the question.

dirn Over a year ago

What version of Python are you using on Ubuntu?

Richard Rublev Over a year ago

python --version Python 3.6.3 :: Anaconda, Inc.

Mike · Accepted Answer · 2018-04-12 06:43:37Z

1

Try to change the URL to, say, http://www.google.com and update Python to the latest version.

answered Apr 12, 2018 at 6:43

Mike

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