[FIXED] Aiohttp, Asyncio: RuntimeError: Event loop is closed

Issue

I have two scripts, scraper.py and db_control.py. In scraper.py I have something like this:

...
def scrape(category, field, pages, search, use_proxy, proxy_file):
    ...
    loop = asyncio.get_event_loop()

    to_do = [ get_pages(url, params, conngen) for url in urls ]
    wait_coro = asyncio.wait(to_do)
    res, _ = loop.run_until_complete(wait_coro)
    ...
    loop.close()
    
    return [ x.result() for x in res ]

...

And in db_control.py:

from scraper import scrape
...
while new < 15:
    data = scrape(category, field, pages, search, use_proxy, proxy_file)
    ...
...

Theoretically, scraper should be started unknown-times until enough of data have been obtained. But when new is not imidiatelly > 15 then this error occurs:

  File "/usr/lib/python3.4/asyncio/base_events.py", line 293, in run_until_complete
self._check_closed()
  File "/usr/lib/python3.4/asyncio/base_events.py", line 265, in _check_closed
raise RuntimeError('Event loop is closed')
RuntimeError: Event loop is closed

But scripts works just fine if I run scrape() only once. So I guess there is some problem with recreating loop = asyncio.get_event_loop(), I have tried this but nothing changed. How I can fix this? Of course those are just snippets of my code, if you think problem can be elsewhere, full code is available here.

Solution

Methods run_until_complete, run_forever, run_in_executor, create_task, call_at explicitly check the loop and throw exception if it's closed.

Quote from docs - BaseEvenLoop.close:

This is idempotent and irreversible

---

Unless you have some(good) reasons, you might simply omit the close line:

def scrape(category, field, pages, search, use_proxy, proxy_file):
    #...
    loop = asyncio.get_event_loop()

    to_do = [ get_pages(url, params, conngen) for url in urls ]
    wait_coro = asyncio.wait(to_do)
    res, _ = loop.run_until_complete(wait_coro)
    #...
    # loop.close()
    return [ x.result() for x in res ]

If you want to have each time a brand new loop, you have t create it manually and set as default:

def scrape(category, field, pages, search, use_proxy, proxy_file):
    #...
    loop = asyncio.new_event_loop()
    asyncio.set_event_loop(loop)    
    to_do = [ get_pages(url, params, conngen) for url in urls ]
    wait_coro = asyncio.wait(to_do)
    res, _ = loop.run_until_complete(wait_coro)
    #...
    return [ x.result() for x in res ]

Answered By - kwarunek