Skip to main content

ASGI specs, helper code, and adapters

Project description

ASGI is a standard for Python asynchronous web apps and servers to communicate with each other, and positioned as an asynchronous successor to WSGI. You can read more at

This package includes ASGI base libraries, such as:

  • Sync-to-async and async-to-sync function wrappers, asgiref.sync
  • Server base classes, asgiref.server
  • A WSGI-to-ASGI adapter, in asgiref.wsgi

Function wrappers

These allow you to wrap or decorate async or sync functions to call them from the other style (so you can call async functions from a synchronous thread, or vice-versa).

In particular:

  • AsyncToSync lets a synchronous subthread stop and wait while the async function is called on the main thread’s event loop, and then control is returned to the thread when the async function is finished.
  • SyncToAsync lets async code call a synchronous function, which is run in a threadpool and control returned to the async coroutine when the synchronous function completes.

The idea is to make it easier to call synchronous APIs from async code and asynchronous APIs from synchronous code so it’s easier to transition code from one style to the other. In the case of Channels, we wrap the (synchronous) Django view system with SyncToAsync to allow it to run inside the (asynchronous) ASGI server.

Threadlocal replacement

This is a drop-in replacement for threading.local that works with both threads and asyncio Tasks. Even better, it will proxy values through from a task-local context to a thread-local context when you use sync_to_async to run things in a threadpool, and vice-versa for async_to_sync.

If you instead want true thread- and task-safety, you can set thread_critical on the Local object to ensure this instead.

Server base classes

Includes a StatelessServer class which provides all the hard work of writing a stateless server (as in, does not handle direct incoming sockets but instead consumes external streams or sockets to work out what is happening).

An example of such a server would be a chatbot server that connects out to a central chat server and provides a “connection scope” per user chatting to it. There’s only one actual connection, but the server has to separate things into several scopes for easier writing of the code.

You can see an example of this being used in frequensgi.

WSGI-to-ASGI adapter

Allows you to wrap a WSGI application so it appears as a valid ASGI application.

Simply wrap it around your WSGI application like so:

asgi_application = WsgiToAsgi(wsgi_application)

The WSGI application will be run in a synchronous threadpool, and the wrapped ASGI application will be one that accepts http class messages.

Please note that not all extended features of WSGI may be supported (such as file handles for incoming POST bodies).


asgiref requires Python 3.5 or higher.


Please refer to the main Channels contributing docs.

To run tests, make sure you have installed the tests extra with the package:

cd asgiref/
pip install -e .[tests]

Maintenance and Security

To report security issues, please contact For GPG signatures and more security process information, see

To report bugs or request new features, please open a new GitHub issue.

This repository is part of the Channels project. For the shepherd and maintenance team, please see the main Channels readme.

Project details

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Filename, size & hash SHA256 hash help File type Python version Upload date
asgiref-3.1.2-py2.py3-none-any.whl (13.4 kB) Copy SHA256 hash SHA256 Wheel py2.py3
asgiref-3.1.2.tar.gz (13.7 kB) Copy SHA256 hash SHA256 Source None

Supported by

Elastic Elastic Search Pingdom Pingdom Monitoring Google Google BigQuery Sentry Sentry Error logging AWS AWS Cloud computing DataDog DataDog Monitoring Fastly Fastly CDN SignalFx SignalFx Supporter DigiCert DigiCert EV certificate StatusPage StatusPage Status page