Configuring APIRouter in FastAPI | Handling larger applications | API documentation | API Development Series Part 4

In this tutorial, we will discuss how to set up an APIRouter in FastAPI to manage bigger applications.

FastAPI is a modern, fast (high-performance), web framework for building APIs with Python 3.6+ based on standard Python type hints. It is one of the fastest Python frameworks available, and it is used by many developers to build efficient and reliable APIs. One of the key features of FastAPI is its ability to manage bigger applications with ease, thanks to the use of APIRouter, which allows developers to organize their API code more effectively.

To get started with setting up an APIRouter in FastAPI, make sure you have FastAPI installed. You can install it using pip:

pip install fastapi

You will also need to install a compatible ASGI server, such as uvicorn, to run your FastAPI application:

pip install uvicorn

Now that you have FastAPI installed, let’s create a basic FastAPI application with two API routes. Create a new Python file, for example, main.py, and add the following code:

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
async def root():
    return {"message": "Hello World"}

@app.get("/items/{item_id}")
async def read_item(item_id: int):
    return {"item_id": item_id}

This is a simple FastAPI application that defines two routes: a root route ("/") that returns a simple message and an items route ("/items/{item_id}") that takes an item_id parameter and returns it in the response. To run this application, you can use uvicorn:

uvicorn main:app --reload

Now, let’s create an APIRouter to manage the routes in a more organized way. Create a new Python file, for example, routes.py, and add the following code:

from fastapi import APIRouter

router = APIRouter()

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

@router.get("/{item_id}")
async def read_item(item_id: int):
    return {"item_id": item_id}

In this code, we have created an APIRouter called router and defined the same two routes as the main.py file. Note that the routes in the APIRouter do not include the path prefix ("/items") as we did in the main.py file.

Now, let’s import and include the APIRouter in the main FastAPI application. Update the main.py file as follows:

from fastapi import FastAPI
from .routes import router

app = FastAPI()
app.include_router(router, prefix="/items")

In this code, we import the router from routes.py and use the include_router method to include it in the main FastAPI application with a prefix of "/items". This means that all routes defined in the router will be accessed through the "/items" prefix.

Now, you can run the updated FastAPI application using uvicorn:

uvicorn main:app --reload

You can access the root route at "http://localhost:8000/items" and the items route at "http://localhost:8000/items/{item_id}".

Using APIRouter in FastAPI allows you to organize your larger applications more effectively by grouping related API routes together. It also helps in maintaining a clean and structured codebase, making it easier to debug and update your API endpoints.

In summary, APIRouter is a powerful feature in FastAPI that helps you manage bigger applications with ease. It allows you to organize your API routes more effectively and maintain a structured codebase. By following the steps outlined in this tutorial, you can start using APIRouter in your FastAPI applications to build efficient and reliable APIs.

This concludes our tutorial on setting up an APIRouter in FastAPI to manage bigger applications. Thank you for reading, and happy coding!