“RuntimeError: This event loop is already running”; debugging aiohttp, asyncio and IDE “spyder3” in python 3.6.5

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Ryan Baumgartner

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May 9, 2018, 9:04:12 PM5/9/18

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Hi All,

I figured that I would try this group out first before submitting a bug in the github repository.

Here is my original problem: https://stackoverflow.com/questions/50243393/runtimeerror-this-event-loop-is-already-running-debugging-aiohttp-asyncio-a

Below is a copy and paste of that description of the problem:

________________________________________________________________________________________________________________________________________

I'm struggling to understand why I am getting the "RuntimeError: This event loop is already running" runtime error. I have tried to run snippets of code from "https://aiohttp.readthedocs.io/en/stable/" however, I keep getting the same issue.

Code snippet from Tutorial:

import aiohttp
import asyncio
import async_timeout

async def fetch(session, url):
    async with async_timeout.timeout(10):
        async with session.get(url) as response:
            return await response.text()

async def main():
    async with aiohttp.ClientSession() as session:
        html = await fetch(session, 'http://python.org')
        print(html)

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

RESULTS from tutorial snippet (while running code from spyder IDE):

RuntimeError: This event loop is already running

<!doctype html>"

... (more html)

Personal code snippet (not from the tutorial referenced above):

import aiohttp
import asyncio
import time

urls = ['https://api.robinhood.com/quotes/c4f6720a-0364-4e7b-8c41-705696759e1a/']

async def fetch(client, url):
    async with client.request('get', url) as response:
        if response.status == 200:
            data = await response.text()
        else:
            data = []
        print(data)
        return(data)

async def get_async_urls(urls):
    async with aiohttp.ClientSession() as client:
        return await asyncio.gather(*(fetch(client, url) for url in urls))

if __name__ == '__main__':
    t0 = time.time()
    loop = asyncio.get_event_loop()
    results = loop.run_until_complete(get_async_urls(urls))
    print(results)
    t1 = time.time()
    total_time = t1-t0
    loop.close()

RESULTS from personal snippet (while running code from spyder IDE):

RuntimeError: This event loop is already running

RESULTS from personal snippet (while running from cmd "python personal_snippet.py") [EXPECTED RESULT]:

{"ask_price":"14.9000","ask_size":100,"bid_price":"14.0100","bid_size":100,"last_trade_price":"14.7900","last_extended_hours_trade_price":"14.7900","previous_close":"14.3600","adjusted_previous_close":"14.3600","previous_close_date":"2018-05-07","symbol":"SURF","trading_halted":false,"has_traded":true,"last_trade_price_source":"consolidated","updated_at":"2018-05-08T20:01:21Z","instrument":"https://api.robinhood.com/instruments/43d56335-f2f6-4711-b650-55be2396f814/"} ['{"ask_price":"14.9000","ask_size":100,"bid_price":"14.0100","bid_size":100,"last_trade_price":"14.7900","last_extended_hours_trade_price":"14.7900","previous_close":"14.3600","adjusted_previous_close":"14.3600","previous_close_date":"2018-05-07","symbol":"SURF","trading_halted":false,"has_traded":true,"last_trade_price_source":"consolidated","updated_at":"2018-05-08T20:01:21Z","instrument":"https://api.robinhood.com/instruments/43d56335-f2f6-4711-b650-55be2396f814/"}']

The above results appear to point to the issue being related to the Spyder IDE.

I have two questions:

Why am I getting this error? It seems like other people do not get this error when running the tutorial code. (Potentially answered: POSSIBLE BUG IN SPYDER3)
This seems to only happen in the spyder IDE. I ran both snippets of code in from the cmd prompt and no error appeared. Thanks to @MikhailGerasimov for the suggestion.
Given that I have two print commands (in the second snippet of code) and that only one set of "data" was printed, then why is data not getting back to the original call (results = loop.run_until_complete(get_async_urls(urls))) (Potentially answered: POSSIBLE BUG IN SPYDER3)
This seems to only happen in the spyder IDE. I ran the second snippet of code in from the cmd prompt and both prints appeared. Thanks to @MikhailGerasimov for the suggestion.

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