uvicorn

<p align="center">
  <img width="320" height="320" src="https://raw.githubusercontent.com/Kludex/uvicorn/main/docs/uvicorn.png" alt='uvicorn'>
</p>

<p align="center">
<em>An ASGI web server, for Python.</em>
</p>

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**Documentation**: [https://uvicorn.dev](https://uvicorn.dev)

**Source Code**: [https://www.github.com/Kludex/uvicorn](https://www.github.com/Kludex/uvicorn)

---

Uvicorn is an ASGI web server implementation for Python.

Until recently Python has lacked a minimal low-level server/application interface for
async frameworks. The [ASGI specification][asgi] fills this gap, and means we're now able to
start building a common set of tooling usable across all async frameworks.

Uvicorn currently supports HTTP/1.1, HTTP/2 and WebSockets.

## Quickstart

Install using `pip`:

```shell
$ pip install uvicorn
```

This will install uvicorn with minimal (pure Python) dependencies.

```shell
$ pip install 'uvicorn[standard]'
```

This will install uvicorn with "Cython-based" dependencies (where possible) and other "optional extras".

In this context, "Cython-based" means the following:

- the event loop `uvloop` will be installed and used if possible.
- the http protocol will be handled by `httptools` if possible.

Moreover, "optional extras" means that:

- the websocket protocol will be handled by `websockets` (should you want to use `wsproto` you'd need to install it manually) if possible.
- the `--reload` flag in development mode will use `watchfiles`.
- `python-dotenv` will be installed should you want to use the `--env-file` option.
- `PyYAML` will be installed to allow you to provide a `.yaml` file to `--log-config`, if desired.

Create an application, in `example.py`:

```python
async def app(scope, receive, send):
    assert scope['type'] == 'http'

    await send({
        'type': 'http.response.start',
        'status': 200,
        'headers': [
            (b'content-type', b'text/plain'),
        ],
    })
    await send({
        'type': 'http.response.body',
        'body': b'Hello, world!',
    })
```

Run the server:

```shell
$ uvicorn example:app
```

---

## Why ASGI?

Most well established Python Web frameworks started out as WSGI-based frameworks.

WSGI applications are a single, synchronous callable that takes a request and returns a response.
This doesn’t allow for long-lived connections, like you get with long-poll HTTP or WebSocket connections,
which WSGI doesn't support well.

Having an async concurrency m