Introduction to FastAPI

Understand the core concepts of FastAPI, how it compares to other web frameworks, and its advantages in building APIs, especially for user authentication.

By Kevin McAleer,    3 Minutes

What is FastAPI?

FastAPI is a modern, fast (high-performance) web framework for building APIs with Python 3.7+ based on standard Python type hints. Its key features include automatic API documentation, data validation, serialization, and asynchronous request handling. FastAPI is designed to make it easy to create a web API that is fast to code, easy to understand, and ready for production.

Core Features of FastAPI

• Speed: FastAPI provides very high performance, on par with NodeJS and Go, thanks to Starlette for the web parts and Pydantic for the data parts.
• Quick Coding: Its design allows for fast development. Define your API using Python type hints, and FastAPI does the rest.
• Automatic Documentation: With FastAPI, you get interactive API documentation automatically generated via Swagger UI and ReDoc.
• Data Validation and Serialization: Uses Pydantic for data validation, serialization, and model binding, ensuring that the data your API receives and sends is correct.
• Asynchronous Support: FastAPI supports asynchronous request handling, making it suitable for high-concurrency situations like handling user authentication and interaction.

Why FastAPI for User Authentication?

Choosing FastAPI for user authentication in your project comes with several benefits:

• Security: FastAPI includes several built-in security features, such as support for OAuth2 with Password (and hashing), JWT tokens, and more, which are crucial for authentication systems.
• Scalability: The asynchronous support makes it easy to scale your authentication system for a high number of requests.
• Developer Experience: The automatic documentation and type hinting make developing and testing your API a breeze.

First Steps with FastAPI

Let’s create a simple FastAPI application to understand its structure:

1. Create a Main Application File:

In your project directory, ensure you have a file named main.py. This file will be the entry point for your FastAPI application.

1. Write Your First FastAPI Code:

Open main.py and add the following code:

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
def read_root():
    return {"Hello": "World"}

1. Run Your FastAPI Application:

Use the following command to run your application:

uvicorn main:app --reload

The --reload flag makes the server restart after code changes. This is useful during development but should be removed in production.

Testing Your API

With your FastAPI application running, visit http://127.0.0.1:8000 in your web browser. You should see a response from your API.

Exploring the Automatic Documentation

FastAPI automatically generates documentation for your API. Access this documentation by visiting http://127.0.0.1:8000/docs for the Swagger UI or http://127.0.0.1:8000/redoc for ReDoc.

Summary

You’ve now created your first FastAPI application and explored some of its core features. In the coming lessons, we’ll dive deeper into building a user authentication system, starting with modeling our user data.

Additional Resources

• FastAPI Official Documentation
• Pydantic Documentation

Lesson Assignment

Experiment with adding another route to your FastAPI application. Try returning different types of data, such as a list or a dictionary with nested data. Reflect on how FastAPI’s automatic documentation updates with your changes.