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AsyncIO Service-based programming.

Project description

Build status BSD License Mode can be installed via wheel Supported Python versions. Supported Python implementations.

Keywords:async, service, framework, actors, bootsteps, graph

What is Mode?

Mode is a library for Python AsyncIO, using the new async/await syntax in Python 3.6 to define your program as a set of services.

When starting a larger project using asyncio, it immediately became apparent that we needed a way to manage the different services running in the program. Questions such as “how do we shutdown the event loop” is frequently answered by telling users to “wait for all coroutines in asyncio.Task.all_tasks”, but we needed more control over what services where stopped, in what order and what services can we safely shutdown without waiting for current operations to complete.

So for us the answer was to create a generic Service class that handles this for us, including creating pretty graphs of active services in the system, and what they are currently doing.

Heavily inspired by Celery/RabbitMQ bootsteps, you could say it’s a less formal version of that, where the graph is built at runtime.

Creating a Service

To define a service, simply subclass and fill in the methods to do stuff as the service is started/stopped etc.:

class MyService(Service):

    async def on_start(self) -> None:
        print('Im starting now')

    async def on_started(self) -> None:
        print('Im ready')

    async def on_stop(self) -> None:
        print('Im stopping now')

To start the service, call await service.start():

await service.start()

Or you can use mode.Worker (or a subclass of this) to start your services-based asyncio program from the console:

if __name__ == '__main__':
    imoport mode
    worker = mode.Worker(MyService(), loglevel='INFO', logfile=None)

It’s a Graph!

Services can start other services, coroutines, and background tasks.

  1. Starting other services using add_depenency:

    class MyService(Service):
        def on_init(self) -> None:
  2. Start a list of services using on_init_dependencies:

    class MyService(Service):
        def on_init_dependencies(self) -> None:
            return [
  3. Start a future/coroutine (that will be waited on to complete on stop):

    class MyService(Service):
        async def on_start(self) -> None:
        async def my_coro(self) -> None:
            print('Executing coroutine')
  4. Start a background task:

    class MyService(Service):
        async def _my_coro(self) -> None:
            print('Executing coroutine')
  5. Start a background task that keeps running:

    class MyService(Service):
        async def _my_coro(self) -> None:
            while not self.should_stop:
                # NOTE: self.sleep will wait for one second, or
                #       until service stopped/crashed.
                await self.sleep(1.0)
                print('Background thread waking up')


You can install Mode either via the Python Package Index (PyPI) or from source.

To install using pip:

$ pip install -U mode

Downloading and installing from source

Download the latest version of Mode from

You can install it by doing the following:

$ tar xvfz mode-0.0.0.tar.gz
$ cd mode-0.0.0
$ python build
# python install

The last command must be executed as a privileged user if you are not currently using a virtualenv.

Using the development version

With pip

You can install the latest snapshot of Mode using the following pip command:

$ pip install


Can I use Mode with Django/Flask/etc.?

Yes! Use gevent/eventlet and use a bridge to integrate with asyncio.

  • aiogevent enables you to run Mode on top of gevent:


    import aiogevent
    import asyncio
    import gevent.monkey
    # if you use PostgreSQL with psycopg, make sure you also
    # install psycogreen and call this pather:
    #  import psycogreen.gevent
    #  psycogreen.gevent.patch_psycopg()
    # Import Django/Flask etc, stuff and use them with Mode.
  • aioeventlet enables you to run Mode on top of eventlet:


    import aioeventlet
    import asyncio
    import eventlet
    # if you use PostgreSQL with psycopg, make sure you also
    # install psycogreen and call this pather:
    #  import psycogreen.eventlet
    #  psycogreen.eventlet.patch_psycopg()
    # Import Django/Flask etc, stuff and use them with Mode.

Can I use Mode with Tornado?

Yes! Use the tornado.platform.asyncio bridge:

Can I use Mode with Twisted?

Yes! Use the asyncio reactor implementation:

Will you support Python 3.5 or earlier?

There are no immediate plans to support Python 3.5, but you are welcome to contribute to the project.

Here are some of the steps required to accomplish this:

  • Source code transformation to rewrite variable annotations to comments

    for example, the code:

         class Point:
             x: int = 0
             y: int = 0
    must be rewritten into::
         class Point:
             x = 0  # type: int
             y = 0  # type: int
  • Source code transformation to rewrite async functions

    for example, the code:

    async def foo():
        await asyncio.sleep(1.0)

    must be rewritten into:

    def foo():
        yield from asyncio.sleep(1.0)

Will you support Python 2?

There are no plans to support Python 2, but you are welcome to contribute to the project (details in question above is relevant also for Python 2).

Code of Conduct

Everyone interacting in the project’s codebases, issue trackers, chat rooms, and mailing lists is expected to follow the Mode Code of Conduct.

As contributors and maintainers of these projects, and in the interest of fostering an open and welcoming community, we pledge to respect all people who contribute through reporting issues, posting feature requests, updating documentation, submitting pull requests or patches, and other activities.

We are committed to making participation in these projects a harassment-free experience for everyone, regardless of level of experience, gender, gender identity and expression, sexual orientation, disability, personal appearance, body size, race, ethnicity, age, religion, or nationality.

Examples of unacceptable behavior by participants include:

  • The use of sexualized language or imagery
  • Personal attacks
  • Trolling or insulting/derogatory comments
  • Public or private harassment
  • Publishing other’s private information, such as physical or electronic addresses, without explicit permission
  • Other unethical or unprofessional conduct.

Project maintainers have the right and responsibility to remove, edit, or reject comments, commits, code, wiki edits, issues, and other contributions that are not aligned to this Code of Conduct. By adopting this Code of Conduct, project maintainers commit themselves to fairly and consistently applying these principles to every aspect of managing this project. Project maintainers who do not follow or enforce the Code of Conduct may be permanently removed from the project team.

This code of conduct applies both within project spaces and in public spaces when an individual is representing the project or its community.

Instances of abusive, harassing, or otherwise unacceptable behavior may be reported by opening an issue or contacting one or more of the project maintainers.

This Code of Conduct is adapted from the Contributor Covenant, version 1.2.0 available at

Project details

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