FastAPI 201: Additional Features of FastAPI

Exploring Advanced Features Beyond Simple API Creation

Photo by Artturi Jalli on Unsplash

Introduction

This article is a follow-up to FastAPI 101: A Comprehensive Tutorial for Building Lightning-Fast APIs. If you are a complete beginner to FastAPI, I encourage you to read that article before this one.

While we’ve covered the basics of building a FastAPI application, there are many additional features that make FastAPI a powerful tool for building APIs. Here are a few examples:

Input validation

FastAPI uses Pydantic models for input validation. This means that you can easily define the expected data structure for your API, and FastAPI will automatically validate incoming requests against that schema. For example, let’s say we wanted to create an endpoint that takes in a user’s name and age. We could define a Pydantic model like this:

from pydantic import BaseModel

class User(BaseModel):
    name: str
    age: int

Then we could use this model in our API endpoint like this:

@app.post("/users/")
async def create_user(user: User):
   # Create user logic here
   return {"message": "User created successfully"}

Now when a client sends a POST request to our `/users/` endpoint, FastAPI will automatically validate the request body against the `User` model, ensuring that the `name` field is a string and the `age` field is an integer.

Dependency Injection

FastAPI supports dependency injection, which allows you to easily share code between different endpoints in your API. For example, let’s say we had a database connection that we wanted to use in multiple endpoints. We could define a dependency like this:

from fastapi import Depends

async def get_database():
   # Create database connection logic here
   return database_connection


@app.get("/users/")
async def get_users(db: Database = Depends(get_database)):
   # Use database connection here
   return {"users": []}

Now when a client sends a GET request to our `/users/` endpoint, FastAPI will automatically call the `get_database` function and pass the resulting database connection to our `get_users` function. This makes it easy to share code between different endpoints without having to duplicate code.

API Documentation

FastAPI generates API documentation automatically based on your code. This means that you can easily provide documentation for your API without having to write any additional code. When you navigate to `http://localhost:8000/docs` in your web browser, you’ll see a Swagger UI that allows you to explore your API and view its documentation.

Conclusion

In this tutorial, we’ve explored some of the additional features that FastAPI offers, including input validation, dependency injection, and API documentation. With these features, FastAPI makes it easy to build fast, efficient, and well-documented APIs in Python. So if you’re looking for a modern and powerful web framework for your next API project, be sure to give FastAPI a try!

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