asyncio support#
New in version 0.1.0.
Callbacks#
Callbacks can also be coroutine functions
(defined using async def
or decorated with
@asyncio.coroutine
). For this to work properly,
the event loop
they belong to must
be specified. This requirement is in place to prevent issues when multiple event
loops are in use (via threads, etc).
The loop can be specified using the Dispatcher.bind_async
method,
or passed as a keyword argument to Dispatcher.bind
.
Examples#
bind_async method#
>>> import asyncio
>>> from pydispatch import Dispatcher
>>> class MyEmitter(Dispatcher):
... _events_ = ['on_state']
... async def trigger(self):
... await asyncio.sleep(1)
... self.emit('on_state')
>>> class MyAsyncListener(object):
... def __init__(self):
... self.event_received = asyncio.Event()
... async def on_emitter_state(self, *args, **kwargs):
... print('received on_state event')
... self.event_received.set()
... async def wait_for_event(self):
... await self.event_received.wait()
>>> loop = asyncio.get_event_loop()
>>> emitter = MyEmitter()
>>> listener = MyAsyncListener()
>>> # Pass the event loop as first argument to "bind_async"
>>> emitter.bind_async(loop, on_state=listener.on_emitter_state)
>>> loop.run_until_complete(emitter.trigger())
>>> loop.run_until_complete(listener.wait_for_event())
received on_state event
bind (with keyword argument)#
>>> import asyncio
>>> from pydispatch import Dispatcher
>>> class MyEmitter(Dispatcher):
... _events_ = ['on_state']
... async def trigger(self):
... await asyncio.sleep(1)
... self.emit('on_state')
>>> class MyAsyncListener(object):
... def __init__(self):
... self.event_received = asyncio.Event()
... async def on_emitter_state(self, *args, **kwargs):
... print('received on_state event')
... self.event_received.set()
... async def wait_for_event(self):
... await self.event_received.wait()
>>> loop = asyncio.get_event_loop()
>>> emitter = MyEmitter()
>>> listener = MyAsyncListener()
>>> # Pass the event loop using __aio_loop__
>>> emitter.bind(on_state=listener.on_emitter_state, __aio_loop__=loop)
>>> loop.run_until_complete(emitter.trigger())
>>> loop.run_until_complete(listener.wait_for_event())
received on_state event
Async (awaitable) Events#
Event (and Property
) objects are awaitable. This allows event
subscription without callbacks in an async environment. The Event
instance
itself must first be obtained using the Dispatcher.get_dispatcher_event
method. Any positional and keyword arguments from the event are returned as a
two-tuple:
async def wait_for_event(event_name):
event = emitter.get_dispatcher_event(event_name)
args, kwargs = await event
return args, kwargs
loop.run_until_complete(wait_for_event('on_state'))
This can also be done with Property
objects
>>> import asyncio
>>> from pydispatch import Dispatcher, Property
>>> class MyEmitter(Dispatcher):
... value = Property()
... async def change_values(self):
... for i in range(5):
... await asyncio.sleep(.1)
... self.value = i
... return 'done'
>>> class MyAsyncListener(object):
... async def wait_for_values(self, emitter):
... # Get the Event object for the Property
... event = emitter.get_dispatcher_event('value')
... # await the event until the value reaches 4
... while True:
... args, kwargs = await event
... instance, value = args
... print(value)
... if value >= 4:
... break
... return 'done'
>>> loop = asyncio.get_event_loop()
>>> emitter = MyEmitter()
>>> listener = MyAsyncListener()
>>> coros = [emitter.change_values(), listener.wait_for_values(emitter)]
>>> loop.run_until_complete(asyncio.gather(*coros))
0
1
2
3
4
['done', 'done']