FastAPI Specific

Input Placement

Put all API input in the endpoint parameters. For request bodies, always use a developer-defined subclass of Pydantic's BaseModel. If there is a single body field, name it payload.

script.python

from pydantic import BaseModelclass Item(BaseModel):    name: str    description: str | None = None    price: float    tax: float | None = None@app.put("/items/{item_id}")async def update_item(item_id: int, payload: Item, q: str | None = None):    ...

For more information on how FastAPI endpoint input works read up here. I would suggest reading from Path Parameters to Request Body.

Structuring API Endpoints

Use a consistent structure in each endpoint:

1. Destructure query parameters, path parameters, or request body.
2. Validate input and return errors if necessary.
3. Call business logic methods or perform simple database queries.
4. Return the response.

script.python

# Destructure query parameters, path parameters, or request body@app.get("/more_route/info/{item_id}", status_code=status.HTTP_200_OK)async def get_info(item_id: int) -> int:    # Validate input    if not valid(item_id):        raise HTTPException(            status_code=status.HTTP_404_NOT_FOUND,            detail=ErrorContext("Item does not exist", "invalid_id", []),        )    # Perform business logic    result = perform_action(item_id)    # Return expected result    return result

Note: ErrorContext is a pydantic class which is discussed in more detail in Error Handling.

Essentially the idea is the purpose of the route code is primarily just to process input and most of the actual logic is performed elsewhere.

Notes

1. Type hint all inputs and outputs for FastAPI endpoints (supports auto-generated docs).
2. Use HTTPException for invalid input errors.
3. Do not wrap the final result in a data key.
4. Use FastAPI's status class for status codes for consistency and readability.
5. Use _ to separate multiple words in route segments (e.g., more_route).
6. Always use the correct HTTP method (know the difference between POST, PUT, and PATCH). reference