How do you run Uvicorn programmatically using uvicorn.run() and uvicorn.Config/Server?

Beyond the CLI, Uvicorn can be configured and launched entirely from Python code. This is useful when you need to customise server startup, integrate it into a larger application, or run it from within an existing async event loop.

import uvicorn

# Method 1: uvicorn.run() - simplest programmatic start
if __name__ == "__main__":
    uvicorn.run(
        "main:app",          # string import path
        host="0.0.0.0",
        port=8000,
        reload=True,         # development only
        log_level="info",
    )

# You can also pass the app object directly (no reload support):
# uvicorn.run(app, host="0.0.0.0", port=8000)

# Method 2: uvicorn.Config + uvicorn.Server - more control
import uvicorn

if __name__ == "__main__":
    config = uvicorn.Config("main:app", port=5000, log_level="info")
    server = uvicorn.Server(config)
    server.run()

# Method 3: Running inside an existing async loop
import asyncio
import uvicorn

async def main():
    config = uvicorn.Config("main:app", port=5000, log_level="info")
    server = uvicorn.Server(config)
    await server.serve()  # use serve() not run() inside async context

if __name__ == "__main__":
    asyncio.run(main())

Important distinction: when passing the app object directly (not a string) to uvicorn.run(), the reload option is not available because the reloader must re-import the module by name. Always use the 'module:attribute' string form when reload=True.

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