Reputation: 1449
I would like to learn how to call a function asynchronously in Python3. I think Tornado can do this. Currently, my code is returning nothing on the command line:
#!/usr/bin/env python3
# -*- coding: utf-8 -*-
async def count(end):
"""Print message when start equals end."""
start = 0
while True:
if start == end:
print('start = {0}, end = {1}'.format(start, end))
break
start = start + 1
def main():
# Start counting.
yield count(1000000000)
# This should print while count is running.
print('Count is running. Async!')
if __name__ == '__main__':
main()
Thanks
Upvotes: 1
Views: 604
Reputation: 17243
To call an async function, you need to provide an event loop to handle it. If you have a Tornado app, it provides such a loop, which allows you to make your handlers asynchronous:
from tornado.web import RequestHandler, url
from tornado.httpserver import HTTPServer
from tornado.ioloop import IOLoop
async def do_something_asynchronous():
# e.g. call another service, read from database etc
return {'something': 'something'}
class YourAsyncHandler(RequestHandler):
async def get(self):
payload = await do_something_asynchronous()
self.write(payload)
application = web.Application([
url(r'/your_url', YourAsyncHandler, name='your_url')
])
http_server = HTTPServer(application)
http_server.listen(8000, address='0.0.0.0')
IOLoop.instance().start()
Outside of a Tornado app you can get the event loop from any number of providers, including the built-in asyncio library:
import asyncio
event_loop = asyncio.get_event_loop()
try:
event_loop.run_until_complete(do_something_asynchronous())
finally:
event_loop.close()
Upvotes: 1