FastAPI – Routers and File Structure #6

FastAPI provides a powerful mechanism for organizing your code through the use of routers and file structures. By using routers, you can divide your API into separate logical components and handle requests more efficiently. In this tutorial, we will explore how to use routers and how to organize your code using a file structure in FastAPI.

Creating a Router
To create a router in FastAPI, you can use the APIRouter class provided by FastAPI. This class allows you to define the routes, dependencies, and operations for a specific logical component of your API. Here’s how you can create a router in FastAPI:

from fastapi import APIRouter

router = APIRouter()

Defining Routes
Once you have created a router, you can define routes inside the router using the router.get(), router.post(), router.put(), router.delete(), and other methods provided by the router object. Here’s an example of how you can define a simple GET route inside a router:

@router.get("/")
async def read_root():
    return {"message": "Hello, World!"}

Mounting a Router
To mount a router to your FastAPI application, you can use the include_router() method provided by your FastAPI app instance. Here’s how you can mount a router to your FastAPI application:

from fastapi import FastAPI

app = FastAPI()

app.include_router(router, prefix="/items", tags=["items"])

In the above code snippet, we are mounting the router to our FastAPI application with a prefix of "/items". This means that all routes defined inside the router will be prefixed with "/items". The tags parameter allows you to group routes in the automatic documentation generated by FastAPI.

File Structure
When building a larger FastAPI application, it’s essential to organize your code effectively using a file structure. A typical file structure for a FastAPI application might look like this:

app/
    └── main.py
    └── routers/
        └── __init__.py
        └── items.py

In this file structure, the main.py file is the entry point of the FastAPI application. The routers directory contains different router modules, with each module representing a logical component of the API. The init.py file inside the routers directory is used to initialize the router modules, while the items.py file contains the router for handling item-related routes.

In your main.py file, you can import and mount routers to your FastAPI application as follows:

from fastapi import FastAPI
from app.routers import items

app = FastAPI()

app.include_router(items.router, prefix="/items", tags=["items"])

By organizing your code using a file structure and routers, you can keep your FastAPI application modular, maintainable, and scalable. Routers help you divide your API into logical components, while a file structure helps you manage your codebase effectively. This tutorial has provided an overview of how to use routers and a file structure in FastAPI and highlighted their benefits in building robust APIs.