The steps to use Python Fast API to publish API services are as follows:

1. Install FastAPI and uvicorn

You can use the pip command to install:

pip install fastapi uvicorn

2. Create a FastAPI application

For example main.py File:

from fastapi import FastAPI
 
app = FastAPI()
 
@app.get("/")
def read_root():
    return {"Hello": "World"}
 
@app.get("/items/{item_id}")
def read_item(item_id: int, q: str = None):
    return {"item_id": item_id, "q": q}
 
@app.post("/items/")
def create_item(item: Item):
    return item

In this example, a FastAPI application is created and three routes are defined: `/`, `/items/{item_id}` and `/items/`.

The `read_root()` and `read_item()` routes use the `@app.get()` decorator to define the `GET` request handler, while

`create_item()` The route uses the `@app.post()` decorator to define the `POST` request handler.

These routes return different response content, including JSON data and FastAPI model objects.

3. Start the FastAPI application

uvicorn main:app --reload

In this example, we use the `uvicorn` command to start the FastAPI application, listen to the `http://localhost:8000` address, and automatically Reload application code changes. If you need to run the application on a different port, you can use the `--port` parameter to specify the port number.

4. Test

For example, use curl or other HTTP client to send a request to your application:

curl http://localhost:8000/
curl http://localhost:8000/items/5?q=somequery
curl -X POST http://localhost:8000/items/ -H "Content-Type: application/json" -d '{"name": "item name", "description": "item description"}'

5. Question

1. If it needs to be called by other machines, you need to specify host

when starting the application. For example: uvicorn main:app --host 192.168.10.8 --port 8888 --reload

2. The meaning of the startup parameter reload

When you use the `--reload` parameter to start the `uvicorn` server, it will monitor changes in the application code and automatically reload the server when the code changes so that you do not have to manually Restart the server.

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