[Python] Keep aiohttp session alive

I'm trying to visit a website every X seconds with parallel and separate sessions, then analyse what is in the response to see if each session should continue or not. However, once the code reaches the second loop it fails.

import asyncio
from aiohttp import ClientSession
import logging
import time

interval = 30
instances = 2
visit_url = 'http://www.example.org'

tasks = []

logging.basicConfig(
format='%(asctime)s.%(msecs)03d %(message)s', # Log in format time.milliseconds {message}
level=logging.INFO, # Use with logging.info()
datefmt='%H:%M:%S') # Display time as Hours:Minutes:Seconds


class StopException(Exception):
pass


async def quit_app(session, task_, reason):
logging.info("[{}] {}.".format(task_, reason))
session.cookies.clear() # Reset cookies
session.headers.clear() # Reset headers
session.close() # End HTTP connection
raise StopException


async def get_status(response):
if "abow" in response:
return "success"
elif "odoap" or "daoscp" in response:
return "waiting"
elif "nullt" in response:
return "fail"
elif "issue" in response:
return "banned"
elif "pending" in response:
return "pending"
else:
return "pending"


async def initialise(headers):
session = ClientSession()
task_ = len(asyncio.Task.all_tasks()) - instances - 1
passed = False
while passed is False:
async with session as session:
async with session.get(visit_url, headers=headers, allow_redirects=True) as initial:
status = await get_status(await initial.text()) # Check HTML for status
if status == "success":
logging.info("[{}] {}.".format(task_, "Success"))
passed = True
elif status == "pending":
logging.info("[{}] {}.".format(task_, "Pending.."))
await asyncio.sleep(interval)
elif status == "waiting":
logging.info("[{}] {}.".format(task_, "Waiting..."))
await asyncio.sleep(interval)
elif status == "banned":
await quit_app(initial, task_, "Banned")
elif status == "fail":
await quit_app(initial, task_, "Failed")


if __name__ == "__main__":
headers = {
'accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8',
'accept-encoding': 'gzip, deflate, br',
'accept-language': 'en-US,en;q=0.9',
'upgrade-insecure-asks': '1',
'user-agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.181 Safari/537.36'
} # Add appropriate headers
start = time.clock()
loop = asyncio.get_event_loop()
for i in range(instances):
task = asyncio.ensure_future(initialise(headers))
tasks.append(task)
loop.run_until_complete(asyncio.wait(tasks))
end = time.clock()
print("Process took {0:.4f} seconds.".format(end - start))


This code returns the following error:

13:56:58.604 Task exception was never retrieved future: Task finished coro= initialise() done, defined at C:/Users/x/PycharmProjects/tests/src/aiohttp_main.py:49 exception=RuntimeError('Session is closed',) RuntimeError: Session is closed
​

I just can't work out how to make the sessions stay alive until I .close() them...

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