What is the difference between WSGI and ASGI for a Python web application?

Distinguishes the synchronous WSGI request contract from ASGI's asynchronous, multi-event application contract.

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WSGI is the traditional synchronous interface between a Python web server and an application: one callable receives a request environment and produces a response. ASGI is an asynchronous interface that can handle a connection as a sequence of events, which supports HTTP, WebSockets, and long-lived async communication. Django can run through either interface, while FastAPI is an ASGI framework. Choosing ASGI does not make synchronous application code nonblocking.

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Distinguishes the synchronous WSGI request contract from ASGI's asynchronous, multi-event application contract.

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Distinguishes the synchronous WSGI request contract from ASGI's asynchronous, multi-event application contract.
WSGI is the traditional synchronous interface between a Python web server and an application: one callable receives a request environment and produces a response. ASGI is an asynchronous interface that can handle a connection as a sequence of events, which supports HTTP, WebSockets, and long-lived async communication. Django can run through either interface, while FastAPI is an ASGI framework. Choosing ASGI does not make synchronous application code nonblocking.
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Under WSGI, concurrency normally comes from multiple processes or threads around synchronous request handlers. ASGI lets one event loop interleave many waiting connections when the entire path uses async-compatible libraries. A blocking database driver or CPU-heavy function still blocks whichever thread or loop executes it. I choose the interface from framework support and traffic shape, not because ASGI is automatically faster for every endpoint.

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Calling ASGI automatically nonblocking
Assuming ASGI makes CPU work parallel
Switching interfaces without auditing middleware and drivers

What is the difference between WSGI and ASGI for a Python web application?

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