Asynchronous Server Gateway Interface
The Asynchronous Server Gateway Interface (ASGI) is a calling convention for web servers to forward requests to asynchronous-capable Python programming language frameworks, and applications. It is built as a successor to the Web Server Gateway Interface (WSGI). Where WSGI provided a standard for synchronous Python application, ASGI provides one for both asynchronous and synchronous applications, with a WSGI backwards-compatibility implementation and multiple servers and application frameworks. Example 
An ASGI-compatible "Hello, World!" application written in Python:async def application(scope, receive, send):
    event = await receive()
    ...
    await send({"type": "websocket.send", ...})Where:

 Line 1 defines an asynchronous function named , which takes three parameters (unlike in WSGI which takes only two), ,  and . is a  containing details about current connection, like the protocol, headers, etc. and  are asynchronous callables which let the application receive and send messages from/to the client. Line 2 receives an incoming event, for example, HTTP request or WebSocket message. The  keyword is used because the operation is asynchronous. Line 4 asynchronously sends a response back to the client. In this case, it is a WebSocket communication. Web Server Gateway Interface (WSGI) compatibility 
ASGI is also designed to be a superset of WSGI, and there's a defined way of translating between the two, allowing WSGI applications to be run inside ASGI servers through a translation wrapper (provided in the asgiref library). A threadpool can be used to run the synchronous WSGI applications away from the async event loop. See also 

 Comparison of web frameworks
 FastCGI
 Python (programming language)
  Web Server Gateway Interface (WSGI)

References

External links 
 Asynchronous Server Gateway Interface Documentation
 Asynchronous Server Gateway Interface Specification

Free software programmed in Python
Python (programming language)