pip install fastapi[all]

from fastapi import FastAPI
app = FastAPI()
@app.get('/')async def root():    return {'message':'hello world!'}

uvicorn.exe main:app --reloadINFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)INFO:     Started reloader process [18784] using statreloadINFO:     Started server process [23504]INFO:     Waiting for application startup.INFO:     Application startup complete. 

from fastapi import FastAPIimport uvicorn
app = FastAPI()
@app.get('/')async def root():    return {'message':'hello world!'}
if __name__ == "__main__":    uvicorn.run(app='main:app',host='127.0.0.1',port=8765,reload=True,debug=True)