Python 3.4 asyncio task doesn't get fully executed -

i'm experimenting python 3.4's asyncio module. since there's no production ready package mongodb using asyncio, have written small wrapper class execute mongo queries in executor. wrapper:

import asyncio functools import wraps pymongo import mongoclient   class asynccollection(object):     def __init__(self, client):         self._client = client         self._loop = asyncio.get_event_loop()      def _async_deco(self, name):         method = getattr(self._client, name)          @wraps(method)         @asyncio.coroutine         def wrapper(*args, **kwargs):             print('starting', name, self._client)             r = yield self._loop.run_in_executor(none, method, *args, **kwargs)             print('done', name, self._client, r)             return r          return wrapper      def __getattr__(self, name):         return self._async_deco(name)   class asyncdatabase(object):     def __init__(self, client):         self._client = client         self._collections = {}       def __getitem__(self, col):         return self._collections.setdefault(col, asynccollection(self._client[col]))   class asyncmongoclient(object):     def __init__(self, host, port):         self._client = mongoclient(host, port)         self._loop = asyncio.get_event_loop()         self._databases = {}      def __getitem__(self, db):         return self._databases.setdefault(db, asyncdatabase(self._client[db])) 

i want execute inserts asynchronously, meaning coroutine executes them doesn't want wait execution complete. asyncio manual states a task automatically scheduled execution when created. event loop stops when tasks done., constructed test script:

from asyncdb import asyncmongoclient import asyncio  @asyncio.coroutine def main():     print("started")     mongo = asyncmongoclient("host", 27017)     asyncio.async(mongo['test']['test'].insert({'_id' : 'test'}))     print("done")  loop = asyncio.get_event_loop() loop.run_until_complete(main()) 

when run script following result:

started done starting insert collection(database(mongoclient('host', 27017), 'test'), 'test') 

there should line indicating mongo query done. can see line when yield from coroutine instead of running using asyncio.async. however, what's odd test entry exists in mongodb when run corouting using asyncio.async, despite fact seems work, don't understand why can't see print statement indicating query has been preformed. despite fact run event loop using run_until_completed, should wait insert task complete, if main coroutine finished before.

asyncio.async(mongo...)) schedules mongo query. , run_until_complete() doesn't wait it. here's code example shows using asyncio.sleep() coroutine:

#!/usr/bin/env python3 import asyncio contextlib import closing timeit import default_timer timer  @asyncio.coroutine def sleep_broken(n):     # schedule coroutine; runs on next yield     asyncio.async(asyncio.sleep(n))  @asyncio.coroutine def sleep(n):     yield asyncio.sleep(n)  @asyncio.coroutine def double_sleep(n):     f = asyncio.async(asyncio.sleep(n))     yield asyncio.sleep(n) # first sleep started     yield f  n = 2 closing(asyncio.get_event_loop()) loop:     start = timer()     loop.run_until_complete(sleep_broken(n))     print(timer() - start)     loop.run_until_complete(sleep(n))     print(timer() - start)     loop.run_until_complete(double_sleep(n))     print(timer() - start) 

output

0.0001221800921484828 2.002586881048046 4.005100341048092 

output shows run_until_complete(sleep_broken(n)) returns in less 2 milliseconds instead of 2 seconds. , run_until_complete(sleep(n)) works should: returns in 2 seconds. double_sleep() shows coroutines scheduled async.async() run on yield from (two concurrent sleeps in parallel) i.e., sleep 2 seconds, not 4. if add delay (without allowing event loop run) before first yield from see yield f doesn't return sooner i.e., asyncio.async doesn't run coroutines; schedules them run.