Idiomatic asyncio utilties
NOTE: This project is under early stage of developement. The public APIs may break version by version.
This is an asynchronous version of contextlib.contextmanager to make it easier to write asynchronous context managers without creating boilerplate classes.
import asyncio
import aiotools
@aiotools.actxmgr
async def mygen(a):
await asyncio.sleep(1)
yield a + 1
await asyncio.sleep(1)
async def somewhere():
async with mygen(1) as b:
assert b == 2Note that you need to wrap yield with a try-finally block to
ensure resource releases (e.g., locks), even in the case when
an exception is ocurred inside the async-with block.
import asyncio
import aiotools
lock = asyncio.Lock()
@aiotools.actxmgr
async def mygen(a):
await lock.acquire()
try:
yield a + 1
finally:
lock.release()
async def somewhere():
try:
async with mygen(1) as b:
raise RuntimeError('oops')
except RuntimeError:
print('caught!') # you can catch exceptions here.You can also create a group of async context managers, which are entered/exited all at once using asyncio.gather().
import asyncio
import aiotools
@aiotools.actxmgr
async def mygen(a):
yield a + 10
async def somewhere():
ctxgrp = aiotools.actxgroup(mygen(i) for i in range(10))
async with ctxgrp as values:
assert len(values) == 10
for i in range(10):
assert values[i] == i + 10This implements a common pattern to launch asyncio-based server daemons.
import asyncio
import aiotools
async def echo(reader, writer):
data = await reader.read(100)
writer.write(data)
await writer.drain()
writer.close()
@aiotools.actxmgr
async def myworker(loop, pidx, args):
server = await asyncio.start_server(echo, '0.0.0.0', 8888,
reuse_port=True, loop=loop)
print(f'[{pidx}] started')
yield # wait until terminated
server.close()
await server.wait_closed()
print(f'[{pidx}] terminated')
if __name__ == '__main__':
# Run the above server using 4 worker processes.
aiotools.start_server(myworker, num_workers=4)It handles SIGINT/SIGTERM signals automatically to stop the server, as well as lifecycle management of event loops running on multiple processes.
import aiotools
i = 0
async def mytick(interval):
print(i)
i += 1
async def somewhere():
t = aiotools.create_timer(mytick, 1.0)
...
t.cancel()
await tt is an asyncio.Task object.
To stop the timer, call t.cancel(); await t.
Please don't forget await-ing t because it requires extra steps to
cancel and await all pending tasks.
To make your timer function to be cancellable, add a try-except clause
catching asyncio.CancelledError since we use it as a termination
signal.
You may add TimerDelayPolicy argument to control the behavior when the
timer-fired task takes longer than the timer interval.
DEFAULT is to accumulate them and cancel all the remainings at once when
the timer is cancelled.
CANCEL is to cancel any pending previously fired tasks on every interval.
import asyncio
import aiotools
async def mytick(interval):
await asyncio.sleep(100) # cancelled on every next interval.
async def somewhere():
t = aiotools.create_timer(mytick, 1.0, aiotools.TimerDelayPolicy.CANCEL)
...
t.cancel()
await t