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Tools for working with async events.

Project description

Tools for publishing and listening for events.

Example Usage


The EventEmitter class can be used directly or as a mix-in to provide the ability to publish and subscribe to events.

import logging
from eventemitter import EventEmitter

log = logging.getLogger(__name__)
emitter = EventEmitter()

def log_event(event, *args, **kwargs):
    log.debug('%s %s %s', event, args, kwargs)

emitter.on('an-event', log_event)
emitter.emit('an-event', 1, 2, keyword=3)
await asyncio.sleep(0)  # 'an-even (1, 2), {keyword: 3}' gets logged.

Listener functions can be defined using def or async def. All listeners are executed in a deferred way. The coro that calls emit must yield for the event to propagate.


If the callback-style model of listening for events is undesirable, an async iterable is provided to offer a second model for handling events.

import logging
from eventemitter import EventEmitter
from eventemitter import EventIterable

log = logging.getLogger(__name__)
emitter = EventEmitter()
iterable = EventIterable(emitter, 'an-event')

async for args, kwargs in iterable:

    log.debug('%s %s %s', event, args, kwargs)

The EventIterable implements the async iterable interface and can be used in conjunction with any of the tools in aitertools.


All tests suites are paired one-to-one with the module they test and live directly adjacent to that same module. All tests are expected to pass for Python 3.5 and above. To run tests use tox with the included tox.ini file or create a virtualenv and install the ‘[testing]’ extras.


Copyright 2015 Kevin Conway

Licensed under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.


Firstly, if you’re putting in a patch then thank you! Here are some tips for getting your patch merged:


As long as the code passes the PEP8 and PyFlakes gates then the style is acceptable.


The PEP257 gate will check that all public methods have docstrings. If you’re adding something new, like a helper function, try out the napoleon style of docstrings.


Make sure the patch passes all the tests. If you’re adding a new feature don’t forget to throw in a test or two. If you’re fixing a bug then definitely add at least one test to prevent regressions.

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